[#263, #314] Undo revert of "Ensure that $terminfo values are valid"

This reverts commit ed4e9af9c41d08876a76a54a3dece174b92c066d.
[Fix #263, Fix #314] Ensure application mode is valid before use
Fallback to standard cabal location on OS X

If ~/Library/Haskell does not exist, fall back to ~/.cabal/bin.

Ideally, we'd parse ~/.cabal/config here, but cabal does not provide an
interface to get configuration settings.
Fix a typo in git documentation
[Fix #335] Prevent rbenv from hashing gems at startup
Fix auto completion for SSH hosts when saved with a non-standard port
Check for the existence of .zcompdump before compiling
[Fix #338] Remove vi jk and kj bindings
[Fix #348] Clarify how GNU utilities are wrapped
Update external completions
Update external syntax-highlighting
Add an alias to ammend a git commit, including the message
[Fix #347] Move 'users' from tag-order to group-order
First pass at personalization