Add Nginx and Puma LWRPs

Added Nginx lwrp which behaves like a toned down apache2_passenger lwrp.

Added Puma lwrp which behaves like unicorn lwrp.

Tweaks to rails lwrp to handle rvm instances and not load chef's embedded ruby if rvm_ruby and rvm_path are defined.

Tested and used to deploy the latest nginx and puma onto a server on ruby 2.1.1

Please see updated readme for new variables added to the lwrps and their functionality.