Menition argparse.version in changelog and docs

CHANGELOG.md

@@ -22,6 +22,7 @@
   for configuring help string autogeneration.
 * Added `help_max_width` property. If set, descriptions in help string
   are automatically wrapped to fit into given number of columns.
+* Argparse version is now available as `argparse.version`.
 
 ### Improvements
 

docsrc/misc.rst

@@ -1,6 +1,11 @@
 Miscellaneous
 =============
 
+Argparse version
+----------------
+
+``argparse`` module is a table with ``__call`` metamethod. ``argparse.version`` is a string in ``MAJOR.MINOR.PATCH`` format specifying argparse version.
+
 Overwriting default help option
 -------------------------------