Move guard gems into optional Gemfile group

CONTRIBUTING.md

@@ -23,7 +23,11 @@ chandler offers the following development and testing commands:
 * `bin/console` loads your working copy of chandler into an irb session
 * `bundle exec chandler` runs your working copy of the chandler executable
 * `rake` executes all of chandler's tests and RuboCop checks
-* `guard` monitors the filesystem and automatically runs tests as you work
+
+A Guardfile is also present, so if you'd like to use Guard to do a TDD workflow, then:
+
+1. Run `bundle install --with guard` to get the optional guard dependencies
+2. Run `guard` to monitor the filesystem and automatically run tests as you work
 
 
 [Issues]: https://github.com/mattbrictson/chandler/issues

Gemfile

@@ -2,3 +2,15 @@ source "https://rubygems.org"
 
 # Specify your gem's dependencies in chandler.gemspec
 gemspec
+
+# Optional development dependencies; requires bundler >= 1.10.
+# Note that these gems assume a Ruby 2.2 environment. Install them using:
+#
+# bundle install --with guard
+#
+group :guard, :optional => true do
+  gem "guard", ">= 2.2.2"
+  gem "guard-minitest"
+  gem "rb-fsevent"
+  gem "terminal-notifier-guard"
+end

chandler.gemspec

@@ -25,13 +25,9 @@ Gem::Specification.new do |spec|
 
   spec.add_development_dependency "bundler", "~> 1.10"
   spec.add_development_dependency "coveralls"
-  spec.add_development_dependency "guard", ">= 2.2.2"
-  spec.add_development_dependency "guard-minitest"
   spec.add_development_dependency "rake", "~> 10.0"
-  spec.add_development_dependency "rb-fsevent"
   spec.add_development_dependency "minitest"
   spec.add_development_dependency "minitest-reporters"
   spec.add_development_dependency "mocha"
   spec.add_development_dependency "rubocop"
-  spec.add_development_dependency "terminal-notifier-guard"
 end