Initial version of ConcurrentDict container via TBB hashmap (#972)

* Initial version of ConcurrentDict container via TBB hashmap

Motivation: SDC relies on typed.Dict implementation in many core
pandas algorithms, and it doesn't support concurrent read/writes.
To fill this gap we add ConcurrentDict type which will be used if
threading layer is TBB.

* Fixing PEP and updating failing import

* Fixing builds, warnings and complying to C++11 syntax

* Fixing PEP and review comments #1

* Fixing remarks #2

* Applying remarks #3

Author: kozlov-alexey

sdc/__init__.py

@@ -50,6 +50,8 @@
 import sdc.extensions.indexes.range_index_ext
 import sdc.extensions.indexes.int64_index_ext
 
+import sdc.extensions.sdc_hashmap_ext
+
 from ._version import get_versions
 
 """