Fix Guard deprecations
Fix Guard deprecations

> Guard::RSpec DEPRECATION WARNING: The :version option is deprecated. Only
> RSpec ~2.14 is now supported.
> Guard::RSpec DEPRECATION WARNING: The :cli option is deprecated. Please
> customize the new :cmd option to fit your need.
> Guard::RSpec DEPRECATION WARNING: The :keep_failed option is deprecated.
> Please set new :failed_mode option value to :keep instead.
> https://github.com/guard/guard-rspec#list-of-available-options

substancelab/rconomic