Added guard and guard-rspec to workflow

searchable.gemspec
added guard and guard-rspec to development dependencies
(guard is a gem that watches for changes and preforms tasks upon change based on configurations)
(guard-rspec is a gem that preforms rspec tests upon changes to the watched files of guard)

Guardfile
added watcher to the spec folder and all of it's subfolders
added watcher to the lib folder and all of it's subfolders
Merge pull request #12 from zachmokahn/02-adding_guard_to_workflow

Added guard and guard-rspec to workflow