Move launchpad import into liftoff.rb
Replace GitHelper with FileManager

FileManager will take any template file (located in /lib/templates) and
move it into the current directory. If it finds an existing file at that
location, it appends the contents of the existing file to the template
after it installs the template.
Don't split the existing file by line

This was needed before because we were making sure that the lines were
unique, but now that we're just appending the existing file to the end
of the template, we don't need to anymore.
Move templates dir to be sibiling of lib