Remove metadata.json and update application readme.
Remove metadata.json and update application readme.

* Metadata.json can be generated with the rake tasks.
* Use 'metadata[cookbook]' and 'metadata_all' to generate .json.
* Application readme needed a few more clarification points.

rapid7-cookbooks/git,protec-cookbooks/git,vinyar/git,pghalliday-cookbooks/git,lostintime/chef-git,vinyar/git,protec-cookbooks/git,h4ck3rm1k3/git,edmunds-chef/git,optimizely/git,optimizely/git,heathsnow/git,grozen/git,heathsnow/git,cookbooks/hw-git,MarcinCebula/git,h4ck3rm1k3/git,tas50/git,Nordstrom/git,jssjr/git,optimizely/git,chef-cookbooks/git,jtimberman/git,fheng/git,h4ck3rm1k3/git,deepak/chef-cookbook-git,glensc/chef-cookbook-git,krobertson/chef-git,brodock/git,hughsaunders/git,myabc/git,heathsnow/git,jssjr/git,veered/git,edmunds-chef/git,joncotton/git,protec-cookbooks/git,andyt/git,JoeyJiao/git,edmunds-chef/git,chef-cookbooks/git,cookbooks/oc-git,jssjr/git,vinyar/git