Support tcsh.

This just adds tcsh to the list of supported shells, with its profile as
~/.tcshrc.
Use correct syntax for csh/tcsh alias.

In these shells, the correct invocation is `alias git hub`, not `alias
git=hub`.
Give correct eval stanza for csh/tcsh.

These shells don't support $() notation, so fall back to `` notation.
Add csh => ~/.cshrc to profiles switch.
Add tests for csh/tcsh alias.

Due to weirdness in my local copy/environment (FreeBSD), attempts to run the
test suite have met with stiff resistance--cucumber reports that git doesn't
exist (!), and /script/test gets confused over core.editor and then bombs
talking about file desciptors.  However, the alias tests in cucumber seem to
pass.
Merge pull request #659 from CaptainHayashi/ch-csh-tcsh-alias

Improve `hub alias` support for csh and tcsh.