run-local-project: on exception, immediately return non-zero return code

This makes sure that 'lein cljsbuild test' exits without 30 second delay.
Introduce TestsFailedException
Throw TestsFailedException when tests fail
Do not print stacktrace for TestsFailedException
using recent version of clojurescript
Change the version uniformly to 0.3.1.
Merge remote-tracking branch 'hsalokor/master' into 0.3.1
Reformat things consistently with surrounding code.
Merge remote-tracking branch 'hsalokor/topic/suppress_stacktrace_on_test_failure' into 0.3.1

Conflicts:
	plugin/src/leiningen/cljsbuild.clj
Add a couple new contributors to the README.
Remove a workaround for CLJS-418.  Closes #164.
Update the README for the requirement of lein 2.1.2.
Use Clojure version 1.5.1 everywhere.
Update the release notes for 0.3.1.
Add convenience docs for :output-wrapper.
Oops, add a period.