Improvements to spec package

[tonchis]

This is a laundry list of improvements I'd like to make to our spec package. We can extract a few of these bullet points into issues of their own, but so far I'm listing them here so we don't lose track of them.

• Print the absolute path of the file where a failure happens.
• Print messages in color.
• When an example ends report OK, SKIP or FAIL depending on the state. Right now it will print OK even with failures.
• Print F when reporting a single failure, and then print all failures (with the print_failure function) when calling @reporter.spec_ended, after everything runs.
• Clean up spec.savi and specs.savi from code we don't need anymore.

[mneumann]

Closing. I have extracted the remaining issues into separate issues #20 and #21

Things already implemented by PR #17:

• Print messages in color.
• When an example ends report OK, SKIP or FAIL depending on the state. Right now it will print OK even with failures.
• Print F when reporting a single failure, and then print all failures (with the print_failure function) when calling @reporter.spec_ended, after everything runs