Add interactive Idris commands to menu

This improves discoverability and helps out users who are new to
Emacs. It was requested by someone in person the other day.
Merge pull request #53 from david-christiansen/more-menu

Add interactive Idris commands to menu
provide idris-kill-buffer which kills the buffer if alive
provide 'q' as keyboard shortcut to destroy the notes; also some cleanups
use idris-kill-buffer
do not use view-mode, since it shadows q - additionally, use idris-kill-buffer
move idris-kill-buffer to idris-common-utils
provide with-struct macro, fixes #54
Merge pull request #56 from hannesm/issue-54

provide with-struct macro, fixes #54
Merge pull request #55 from hannesm/minor-fixes

Minor fixes