Support type search

This adds straightforward support for :search.

It also rebinds a few keys by default to better follow Emacs conventions
as well as SLIME's. This is together with :search support because it
fits into those keybindings.
Merge pull request #172 from david-christiansen/type-search

Support type search
Check for buffer load marker in idris-load-sync

Fixes #174.
Merge pull request #175 from david-christiansen/issue/174

Check for buffer load marker in idris-load-sync
Remove the need for a ; after tactics in prover
Highlight the "postulate" keyword
Merge pull request #176 from david-christiansen/postulate-highlight

Highlight the "postulate" keyword
Close prover windows after qed
Readable timestamps in *idris-events*
Launch the prover from right-click menu on metavariables
Working prover that can save proofs
Be more selective about where Idris tries to make buffers clickable
Merge pull request #179 from david-christiansen/clickable-module-selectivity

Be more selective about where Idris tries to make buffers clickable
Merge pull request #178 from david-christiansen/prover

Make the prover work
Don't show error on empty REPL command.

Instead, just give a new prompt.
Docstring
Major simplification of marker protocol in REPL buffer

This makes it easier to make the prover interact well with the REPL.
Make prover window more reliable
Update metavariable list after proving something
Add missing cleanup to idris-quit.