Doc updates: dependency versions, standard links

Author: kislyuk

README.rst

@@ -4,18 +4,17 @@ SignXML: XML Signature in Python
 *SignXML* is an implementation of the W3C `XML Signature <http://en.wikipedia.org/wiki/XML_Signature>`_ standard in
 Python. This standard (also known as XMLDSig and `RFC 3275 <http://www.ietf.org/rfc/rfc3275.txt>`_) is used to provide
 payload security in `SAML 2.0 <http://en.wikipedia.org/wiki/SAML_2.0>`_ and
-`WS-Security <https://en.wikipedia.org/wiki/WS-Security>`_, among other uses.  Three versions of the
-standard exist (`Version 1 "Second Edition" <http://www.w3.org/TR/xmldsig-core/>`_, `Version 1.1
-<http://www.w3.org/TR/xmldsig-core1/>`_, and `Version 2.0 <http://www.w3.org/TR/xmldsig-core2>`_). *SignXML* implements
-all of the required components of the standard, and most recommended ones. Its features are:
+`WS-Security <https://en.wikipedia.org/wiki/WS-Security>`_, among other uses. Two versions of the standard exist
+(`Version 1.1 <http://www.w3.org/TR/xmldsig-core1/>`_ and `Version 2.0 <http://www.w3.org/TR/xmldsig-core2>`_).
+*SignXML* implements all of the required components of the standard, and most recommended ones. Its features are:
 
 * Use of `defusedxml.lxml <https://bitbucket.org/tiran/defusedxml>`_ to defend against common XML-based attacks when
   verifying signatures
 * Extensions to allow signing with and verifying X.509 certificate chains, including hostname/CN validation
 * Support for exclusive XML canonicalization with inclusive prefixes (`InclusiveNamespaces PrefixList
   <http://www.w3.org/TR/xml-exc-c14n/#def-InclusiveNamespaces-PrefixList>`_, required to verify signatures generated by
   some SAML implementations)
-* Modern Python compatibility (2.7-3.5+ and PyPy)
+* Modern Python compatibility (2.7-3.6+ and PyPy)
 * Well-supported, portable, reliable dependencies: `lxml <https://github.com/lxml/lxml>`_, `defusedxml
   <https://bitbucket.org/tiran/defusedxml>`_, `cryptography <https://github.com/pyca/cryptography>`_, `eight
   <https://github.com/kislyuk/eight>`_, `pyOpenSSL <https://github.com/pyca/pyopenssl>`_
@@ -37,11 +36,11 @@ Note: SignXML depends on `lxml <https://github.com/lxml/lxml>`_ and `cryptograph
 +--------------+---------+-------------------------------------------------------------------------------------------------+
 | OS           | Python  | Command                                                                                         |
 +==============+=========+=================================================================================================+
-| Ubuntu 16.04 | Python 2| ``apt-get install python-dev python-cffi libxml2-dev libxslt1-dev libssl-dev``                  |
-|              |         | ``python-lxml python-cryptography python-openssl python-certifi python-defusedxml``             |
+| Ubuntu 16.04,| Python 2| ``apt-get install python-dev python-cffi libxml2-dev libxslt1-dev libssl-dev``                  |
+| 18.04        |         | ``python-lxml python-cryptography python-openssl python-certifi python-defusedxml``             |
 +--------------+---------+-------------------------------------------------------------------------------------------------+
-| Ubuntu 16.04 | Python 3| ``apt-get install python3-dev python3-cffi libxml2-dev libxslt1-dev libssl-dev``                |
-|              |         | ``python3-lxml python3-cryptography python3-openssl python3-certifi python3-defusedxml``        |
+| Ubuntu 16.04,| Python 3| ``apt-get install python3-dev python3-cffi libxml2-dev libxslt1-dev libssl-dev``                |
+| 18.04        |         | ``python3-lxml python3-cryptography python3-openssl python3-certifi python3-defusedxml``        |
 +--------------+---------+-------------------------------------------------------------------------------------------------+
 | Ubuntu 14.04 | Python 2| ``apt-get install python-dev python-cffi libxml2-dev libxslt1-dev libssl-dev``                  |
 +--------------+---------+-------------------------------------------------------------------------------------------------+
@@ -163,7 +162,6 @@ Links
 * `Package distribution (PyPI) <https://pypi.python.org/pypi/signxml>`_
 * `Change log <https://github.com/XML-Security/signxml/blob/master/Changes.rst>`_
 * `List of W3C XML Signature standards and drafts <http://www.w3.org/TR/#tr_XML_Signature>`_
-* `W3C Recommendation: XML Signature Syntax and Processing (Second Edition) <http://www.w3.org/TR/xmldsig-core/>`_
 * `W3C Recommendation: XML Signature Syntax and Processing Version 1.1 <http://www.w3.org/TR/xmldsig-core1>`_
 * `W3C Working Group Note: XML Signature Syntax and Processing Version 2.0 <http://www.w3.org/TR/xmldsig-core2>`_
 * `W3C Working Group Note: XML Security 2.0 Requirements and Design Considerations <https://www.w3.org/TR/2013/NOTE-xmlsec-reqs2-20130411/>`_