changed shebang to #!/usr/bin/env bash

previously was #!/bin/env bash (which doesn't exist on ubuntu)
add .python-version and .python-env files, fixed a typo and added inline documentation to bin/pyenv-autoenv
added requirements.txt with virtualenv and virtualenvwrapper
Merge branch 'release/0.0.2'
git flow release finish 0.0.2: added .python-version, .python-env and requirements.txt, edited bin/pyenv-autoenv for clarity and added brief inline documentation