add p to Environment Management section

Author: vinta

README.md

@@ -93,6 +93,7 @@ A curated list of awesome Python frameworks, libraries and software. Inspired by
 
 *Libraries for Python version and environment management.*
 
+* [p](https://github.com/qw3rtman/p) - Dead Simple Interactive Python Version Management.
 * [pyenv](https://github.com/yyuu/pyenv) - Simple Python version management.
 * [virtualenv](https://pypi.python.org/pypi/virtualenv) - A tool to create isolated Python environments.
 * [virtualenvwrapper](https://pypi.python.org/pypi/virtualenvwrapper) - A set of extensions to virtualenv.