First draft of basic zsh completion
zsh-completion module for kerl
Update readme
Update README.md

Formatting
Add TODO comment for _kerl
Change to env var restoration in activate script

Change to direct removal of the pre-known addition from $PATH and
$MANPATH
Merge pull request #57 from sanmiguel/master

Add zsh completion
Merge pull request #58 from sanmiguel/improve-deactivate

Change of env var restoration mechanism in activate script