avoid spurious 'nil' output from emacs notifier

The emacs notifier was causing guard to output a line saying 'nil'
every time emacsclient was invoked.  Now the stdout from emacsclient
is discarded.
Merge pull request #406 from aspiers/emacs-nil-fix

Avoid spurious 'nil' output from emacs notifier
Improve commands implementation, docs & specs
Update CHANGELOG
Use Ruby 1.8 Hash style
Add coveralls.io support.
Ruby 1.8 hash style...
Add FileNotifier

FileNotifier writes guard notification results to a file. This allows
users to handle notifications in a more custom way (think guard-shell).
Change work dir to the `watchdir`.
Document FileNotifier
Ruby 1.8 hash syntax
Add changelog entry
Merge remote-tracking branch 'origin/pr/407'

Conflicts:
	CHANGELOG.md
Double quotes are needed for escape sequences. [ci skip]
Add options to Notifier .available?
FileNotifier uses new available? options to determine if a path was given
Release 1.7.0
Fix CHANGELOG. [ci skip]
Move guard-rspec to the development group

[ci skip]
Pimp Changelog & Readme

[ci skip]