add scala-version to generated .ensime command

The next version of ensime will be cross-built to support both 2.10 and 2.11; this value will tell ensime which build of ensime to use
generate .ensime via 'sbt ensime'

The space was awkward.
sbt "ensime generate" still works
sbt "ensime help" will show help.
Merge pull request #22 from SpinGo/master

add scala-version to generated .ensime command
Update README.md
explicit sbt version
Merge pull request #26 from ensime/explicit_sbt_version

explicit sbt version