Use Sphinx style as default

This change affects to the default template and also the vim source file
to archive following result:

    def foo(n: int, m: str) -> int:
        """foo

        :param n:
        :type n: int
        :param m:
        :type m: str

        :rtype: int
        """
        pass

The custom template follow Google style still works fine.

I prefer to keep an empty line between `rtype` and `param` because:
- It's easier to handle the logic.
- It look better IMHO.

Though, there's a small issue that is not easy to fix. See the following
example:

    def foo(n: int, no_type) -> int:
        """foo

        :param n:
        :type n: int
        :param no_type

        :rtype: int
        """
        pass

Notice that there's no colon (`:`) after `no_type`.

Author: letientai299

autoload/pydocstring.vim

@@ -168,12 +168,12 @@ function! s:builddocstring(strs, indent, nested_indent)
             let argTemplate = s:readtmpl('arg')
             let argTemplate = join(s:readtmpl('arg'), '')
             let argParts = split(arg, ':')
-            let argTemplate = substitute(argTemplate, '{{_name_}}', argParts[0], '')
-            let arg = substitute(argTemplate, '{{_type_}}', argParts[1], '')
+            let argTemplate = substitute(argTemplate, '{{_name_}}', argParts[0], 'g')
+            let arg = substitute(argTemplate, '{{_type_}}', argParts[1], 'g')
           endif
 
           let template = substitute(template, '{{_args_}}', arg, 'g')
-          let template = substitute(template, '{{_lf_}}', '\n', '')
+          let template = substitute(template, '{{_lf_}}', '\n', 'g')
           let template = substitute(template, '{{_indent_}}', a:indent, 'g')
           let template = substitute(template, '{{_nested_indent_}}', a:nested_indent, 'g')
           call add(docstrings, a:indent . template)

template/pydocstring/arg.txt

@@ -1 +1 @@
-{{_name_}} ({{_type_}})
+{{_name_}}:{{_lf_}}{{_indent_}}:type {{_name_}}: {{_type_}}

template/pydocstring/multi.txt

@@ -1,4 +1,4 @@
 """{{_header_}}
-:param {{_args_}}:
-return ({{_returnType_}}):
+:param {{_args_}}
+:rtype: {{_returnType_}}
 """

test/type-hint.vader

@@ -11,7 +11,7 @@ Expect python:
     def foo() -> str:
         """foo
 
-        return (str):
+        :rtype: str
         """
         pass
 
@@ -25,9 +25,9 @@ Expect python:
     def foo(sample_var) -> str:
         """foo
 
-        :param sample_var:
+        :param sample_var
 
-        return (str):
+        :rtype: str
         """
         pass
 
@@ -41,10 +41,10 @@ Expect python:
     def foo(arg1, arg2) -> str:
         """foo
 
-        :param arg1:
-        :param arg2:
+        :param arg1
+        :param arg2
 
-        return (str):
+        :rtype: str
         """
         pass
 
@@ -59,9 +59,10 @@ Expect python:
     def foo(n: int) -> int:
         """foo
 
-        :param n (int):
+        :param n:
+        :type n: int
 
-        return (int):
+        :rtype: int
         """
         pass
 
@@ -76,10 +77,12 @@ Expect python:
     def foo(n: int, m: str) -> int:
         """foo
 
-        :param n (int):
-        :param m (str):
+        :param n:
+        :type n: int
+        :param m:
+        :type m: str
 
-        return (int):
+        :rtype: int
         """
         pass
 
@@ -95,10 +98,11 @@ Expect python:
     def foo(n: int, arg) -> int:
         """foo
 
-        :param n (int):
-        :param arg:
+        :param n:
+        :type n: int
+        :param arg
 
-        return (int):
+        :rtype: int
         """
         pass