Update the Modulefile summary.

Update the .gemfile to source gems from https://rubygems.org to fix a
Travis/bundler warning.
Update the .fixtures.yml for proper YAML formatting.
Remove execute bits from rspec test files.
Remove support for the beta version of Impala.

Impala is now GA and ships alongside CDH so we no longer have to treat
it special.
Update the scm-config.ini template.

Now support the CM 4.6 version of the scm-config.ini file.