Update mocha require statement

Deprecation message indicates that this is now the correct way to
require mocha.
Remove the bigdecimal gem dependency

This does not seem to be used in the existing source code, so I am
going to try out removing it. It seems to be causing an error during
TravisCI execution, and this might fix that.

If this turns out to be necessary, then I'll revert this commit in
its PR.
TEMP Adding debugging flag to see the results in TravisCI

This commit should not be merged.
To try and determine what is going wrong with the TravisCI build I
want to try getting the debugging output.
This commit will be removed after that.