Bump slimerjs version to 0.9.4
Update tests

* update the test for version string
* remove the test for exit codes - SlimerJS does not return exit code

@see http://docs.slimerjs.org/nightly/api/slimer.html#exit
Add .swp files to gitignore
Merge pull request #9 from macbre/v0.9.4

Bump slimerjs version to 0.9.4