Remove gem executables, since there aren't any
Reorganize gemspec according to common convention
Update the way files are added in the gemspec

Since the gem is packaged based on this file list, it seems pertinent to
only include files that users might want to see when they install the
gem, so let's explicitly list those files from the root that we want to
include.

Also, let's use Ruby globbing instead of `git ls-files` so it's all
in-Ruby calls.

Note: `.yardopts` is included explicitly to show the file list on
rdoc.info if later added. See [this Twitter conversation][twitter].

[twitter]: https://twitter.com/lsegal/status/270950893875245057
Remove lines adding lib to the load path

RSpec does this automatically now.
Don't require rubygems in spec_helper
Add simple RSpec.configure block for expect syntax

Without the configure block, [mutant][mutant] was raising an error. I'm
interested in mutation testing our test suite, so thought this would be
the simplest thing to add to get that working. It also enforces the
expect syntax, which is a nice side benefit.

[mutant]: https://github.com/mbj/mutant
Merge pull request #226 from michaelherold/update-some-configuration

Update some configuration