Truncate post slugs when importing from Tumblr.

Fixes #481.
pygments options for pygments.rb
Added a configuration variable: keep_files (default: ['.git']), based on this pull request: https://github.com/mojombo/jekyll/pull/556
removed puts
faster_lsi: Massively accelerate LSI performance.

Currently, Classifier::LSI rebuilds the index every time an entry is
added.  This runs into massive performance overheads on my website;
theoretically, disabling automatic index rebuilds, and explicitly
rebuilding the LSI index at the end of the LSI repopulation should
speed things up nicely.

As a side note, here, I use pandoc-ruby to provide a more featureful
Markdown transformer, so be mindful that the numbers I quote here have
artifically imposed I/O overheads.

With just the 76 posts I wrote this year (abysmal, I know), I come up
with the following figures:

    Without faster_lsi:
      jekyll --lsi  16.91s user 0.88s system 97% cpu 18.302 total
    With faster_lsi:
      jekyll --lsi  2.72s user 0.77s system 88% cpu 3.940 total

With 109 posts, we begin to see even better improvements:

    Without faster_lsi:
      jekyll --lsi  51.00s user 1.47s system 98% cpu 53.060 total
    With faster_lsi:
      jekyll --lsi  5.04s user 1.12s system 91% cpu 6.735 total

At this point, we begin to see I/O overheads being slower than LSI
when faster_lsi is active.  I call that fairly conclusive.  But wait,
there's more.  I have 273 posts lying around... I wonder what happens
if I feed them all in.  With faster_lsi, it was nice and clippy.
Without it, I simply gave up, and went and refilled my cup of tea.
And it was still going.

    Without faster_lsi:
      jekyll --lsi  1277.86s user 10.90s system 99% cpu 21:30.29 total
    With faster_lsi:
      jekyll --lsi  34.62s user 4.43s system 96% cpu 40.430 total

That is, in anyone's books, a major improvement.  Note, however, that
I don't know just how well this will perform with `jekyll --auto`
because I don't know how it does the LSI rebuilds.  I _think_ (but
please, don't commit me on this) that the LSI is rebuilt every time
Jekyll picks up a file change.

So, all up, the performance improvement is massive, and scales
depending on how many files you have.  At the last point, the
improvement is just on 3200%.

A more optimal solution would be to cache the LSI index and/or content
data somehow.  I'll leave that to when faster_lsi takes over ten
minutes to run.
use Array.join instead of Array.inject, add .svn to defaults
Add commander dependency
Add bin/jekyll2 and initial BuildCommand

The `BuildCommand` class is responsible for handling the building of the site.
It can also optionally watch for changes to files and regenerate the site if
needed.

The `Command` class holds any methods which are used by any command
implementation.
Add initial serve command

The `ServeCommand` will let you serve your site locally for development. You
can specify `--port`, `--host` and `--baseurl` options if you wish to change the
defaults.

Additionally the `BuildCommand` will be called before the processing of the
serve command, this makes sure that the site is actually built. This means you
are able to pass the `--watch` option to auto-regenerate your site, even while
serving it locally.
Update global options and command descriptions
Update loop position so trap handler is used
Add missing ] in self.watch string
Update Jekyll.configuration to convert symbol keys

Because Commander uses symbol keys in the options hash and I don't want to go
back backport every hash string key to symbols in Jekyll. :star:
Update the sym->str key conversion
Update to make the help command default
Rename Args to Options in command docs
Add TODOs for current switches
Add LSI option for build and serve commands
Remove comments
Add initial MigrateCommand

Not all migrators can actually be calld from the comand line. Some require
options which are not passed in and have to be called by other means.