Remove hardcoded path to remote rake

Now that the production server has a sane rake, we need to remove the stupid
1.8 gems path prefix from our remote calls. We can now just do 'rake',
thankfully.

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>
Merge pull request #183 from MosesMendoza/maint/master/fix_rake_path

Remove hardcoded path to remote rake