Merge pull request #491 from yawaramin/issues/235

FscHelper: separate `fsc` function with exit code, &c.
Run cleanup over FSCHelper
Make the scs local - do not reuse in multiple compile runs
Some more cleanup in the FSCHelper
Adding FSC helper to release notes
Bump version to 3.1.0
Add description for FSCHelper
Merge branch 'master' of https://github.com/fsharp/FAKE
Try to standardize Fsc docs
Try to standardize docs
GuardedAwaitObservable was made public by accident - this was fixed
Fsc: add tutorial for Fsc tasks, issue #235
ReFake: implement incremental build logic DSL

Relies on the new 'fsc' compile function.