Puppetfile search & replace

I have updated the regex in  lib/reaktor/r10k/puppetfile.rb so reaktor can update the Puppetfile base on the repository ssh url instead of the module name so the module name does not have to match the repository name. This was causing problems for working with puppet labs module for instance.  (e.g module: apache, url:  git@github.com:puppetlabs/puppetlabs-apache.git)
 
There were a bug in the documentation I have fixed as well: REAKTOR_PUPPETFILE_GIT_URL does not exit in the code. It is the PUPPETFILE_GIT_URL environment variable which need to be exported.