Working go tests
Fix problem with go invocation

The current directory seems to be somewhat important, since the solution
and the test filenames need to match up. Easiest to just cd there and
trigger the runner on the local files.
Don't use `let` for a `before(:all)` block
Only run Go tests explicitly
Add Ruby to rake spec:language
Merge pull request #79 from skanev/golang-test-runner

Golang test runner