Rewrite sed commands to be less platform dependent.

MacOS doesn't ship with version of sed that includes (convenient)
GNU extensions. We need to rewrite sed commands into a little bit more
ugly form to make them less platform dependent.
Merge remote-tracking branch 'gkossakowski/master'
Merge branch 'master' of https://github.com/gkossakowski/sbt-name-hashing-cases into gkossakowski-changes
Fix sed incompatibility
Merge pull request #1 from fernandoacorreia/gkossakowski-changes

Fix sed incompatibility