Bump versions
Avoid deprecation/feature warnings

This commit adds -deprecation and -feature to scalacOptions and fix source code to avoid deprecation/feature warnings.
Since scala/scala-continuations#8 is already working on the usages of deprecated CompilationUnit, this commit does not fix them.
Use reporter.warning instead of deprecated unit.warning
Update sbt to 0.13.6
Update the scala version to 2.11.0 in .travis.yaml

Testing with 2.11.0-SNAPSHOT results "UNRESOLVED DEPENDENCIES".
Merge pull request #9 from sumito3478/fix-warnings

Avoid deprecation/feature warnings