Store Guardfile source (:inline, :custom, :default)

This will ensure default or custom Guardfiles won’t be considered as
inline when re-evaluating.
Add an attribute reader for :guardfile_path
Don't store evaluated Guardfile in options[: guardfile_contents]

Store it in the instance var guardfile_contents instead.
Merge pull request #567 from kiela/master

Delete specifying RSpec dependency twice
Merge pull request #568 from guard/fix-540

Fix #540 & #566: Guardfile re-evaluation
Fix syntax highlighting.
Include "The MIT License (MIT)" in the LICENSE

[ci skip]
Make minimum listen version 2.7

Because versions of listen < 2.7 have a bug where the rails console and tests stop responding to SIGINT, and this is affecting all of our projects that use guard
Merge pull request #576 from shevaun/patch-1

Make minimum listen version 2.7
Provide more helpful errors when performing DSL actions that only make sense within a guard block.
Support for top-level watch expressions via the DSL
Merge pull request #578 from nevir/top-level-watches

Top level watches
Release 2.6.0
Fix indentation
Merge pull request #580 from deivid-rodriguez/patch-1

Fix indentation
Ensure not to call `tmux` when running specs.
Fixs notifier when display_on_all_clients is true

line 254 no spaces '\#{client_tty}' are important
Remove null terminal from clients list

Starting tmux in control mode ```tmux -C``` results in (null) being
listed in client list ```tmux list-clients -F '#{client_tty}'```
Update README.md

R.I.P @netzpirat
correctly match notification type to urgency argument in notifysend
notifier