Remove "archive" Rake task

I'm not going to maintain the "releases" branch anymore, for reasons
described in the README on that branch, so this Rake task no longer has
a reason to exist.

Signed-off-by: Wincent Colaiuta <win@wincent.com>
Debounce key-presses to improve responsiveness

This idea is based on a patch from Yiding Jia, with some additional
logic added to ensure that potentially expensive matching only occurs
when really needed (ie. we don't re-match just because you hit a cursor
up or down key).

Not sure what the sweet spot for the debounce interval is, so starting
with 50ms, and making it configurable. I suspect that on really large
hierarchies you might want this to be higher (say, 100, 150 or even
200ms) in order to reduce the likelihood of unwanted match computations
kicking off just because you happened to slow a little in typing.

Note the use of augroups here to ensure that we don't keep adding more
and more autocmds to the buffer (depending on the platform, the buffer
will be cleaned up with bwipeout! or bunload!; in practice the same
buffer is usually used over and over again, so we wind up with a single
autocmd assigned to a buffer designated as `<buffer=2>` or similar).

Signed-off-by: Wincent Colaiuta <win@wincent.com>
Fix typo in Controller#delete method

This typo was originally introduced in commit ff72bd9bdffaf84247288a0.

Signed-off-by: Wincent Colaiuta <win@wincent.com>