Use bower to manage jre deps.

Should Fix #70 and probably a few others.

As discussed with @jdegoes, just bundle the jre with the nw build since we are constantly running into these java issues.

@jdegoes, in the end it made more sense to have it in here since this allows us to use bower to automate pulling down/unzipping the files and whatever else might be needed for signing each release, vs trying to automate it with bitrock.