Create a new tmux session if none exists
Fix typo

Signed-off-by: Sorin Ionescu <sorin.ionescu@gmail.com>
[Fix #724] Unquote variable

Signed-off-by: Sorin Ionescu <sorin.ionescu@gmail.com>
Use $GNUPGHOME if it exists
[Fix #732] Replace $GREP_OPTIONS with an alias
Merge branch 'master' of https://github.com/sorin-ionescu/prezto