Merge pull request #709 from ZyX-I/zsh-vi-mode

Add support for modes to shell bindings
Merge pull request #706 from ZyX-I/better-errors

Better error handling
Add powerline.tcsh

Ref #762
Add space to rprompt

According to tcsh documentation `%{%}` must not be the last segment.

Note: this means that right prompt has *two* characters between its end and 
terminal emulator border.
Add tcsh tests
Fix tcsh escaping
Install tcsh in travis
Add directories test