Clean packages metadata when installing nightly

Make sure to clean and fetch clean packages metadata to avoid package
not found install errors.
Merge pull request #85 from elyezer/metadata-clean

Clean packages metadata when installing nightly
Added simple os detection
Merge pull request #55 from adamruzicka/os-detection

Added simple os detection
A few small fixes
Merge pull request #88 from daviddavis/temp/20141105122001

A few small fixes
capture installer logs on devel install

as foreman-debug is not available, nor katello
Merge pull request #89 from jlsherrill/devel_log

capture installer logs on devel install
Update to allow EL7 bats to run.
Merge pull request #91 from ehelms/allow-el7-bats

Update to allow EL7 bats to run.
Add support for plugins