* Update requirements.txt to pin charm-tools to 2.8.3
* Update tox.ini to change the build parameters.
* This upgrades from <2.7 which adds reproducible charms
* Bug was fixed that controlled the default output directory
doesn't get 'builds' appended. The tox change puts it
back so that stable & master both build to the same
directory. This may be reviewed in the future.
Change-Id: Ic451da4b61bece4b037b70b36aaf1ddec8ec873e
437e775c3f