Add ERB parsing to YAML configuration

This allows you to insert shell configuration or other Ruby
code in ERb tags in your YAML configuration.
Merge branch 'master' of github.com:vaneyckt/Jently into erbified-yaml-configuration
small ERB support addendums
don't have pull requests yaml file use erb
add parentheses
don't break backwards compatibility
improve config docs
Merge pull request #14 from vaneyckt/erbified-yaml-configuration

Reference PR - Erbified yaml configuration