Centralizes dependencies in gemspec

* Removes deps from gemfile
* Removes growl entirely- not needed
* Updates gem dep versions
Updates years in LICENSE file
Updates rake tasks and spec_helper for rspec
Use guard-compat

* Updates code to use Guard::Plugin instead of Guard::Guard
* Updates spec code to use 'expect' instead of 'should'
Remove Guardfile from lib
Updates README

* Improves formatting
Bumps version to 1.0.0

Going from Guard::Guard to Guard::Plugin represents a major underlying
change, and re-setting dependencies across major version boundaries
makes it so that we're bumping the major version on this gem as well.
Updates gem metadata

* Bumps version to 1.0.1 to aid testing
* Adjusts dep versions