Trigger rubber:config after deploy:update_code

Also added logic to skip rubber:config and deploy:assets:precompile
during db role bootstrapping.

This commit doesn't break normal deploys (including deploy:migrations
or deploy:migrate) with a deploy.rb from old vulcanizations but
boostrap_db may fail if the assets task requires a database connection.
Re-vulcanizing to replace it with the new deploy.rb will fix this
though.
Added bc to the core packages list since we use it to compare version numbers inside of bash deploy scripts.
Handle setting up the root user on machines where the inital SSH user has a password set.

Apparently the Canonical EC2 AMIs don't have a password set for the ubuntu user by default, so there was no need to prompt for a sudo password.  Prompting for the sudo password was broken because we needed the inital SSH user's password, not the deploying user's password.
Added a generic cloud provider for using rubber with physical hardware, virtual machines, or otherwise unsupported cloud providers.
Merge pull request #277 from rubber/simpler_rubber_config_callback

Trigger rubber:config after deploy:update_code
Merge branch 'add_generic_provider'
Make sure we can always connect to postgres on the internal IP, no matter what the subnet.
Allow using S3 with the generic cloud provider.
It's perfectly legitimate to create an EC2 instance with a nil availability zone, so the '||' with the region value was screwing things up.
Preparing the 2.4.0 release.
Oops.  I forgot to commit the tests.
Test against Ruby 2.0.0.
Work around a bug with fog & excon.

See https://github.com/fog/fog/issues/1832 for more details.
Only try to silence sidekiq if current_path actually exists.
We need to go after the symlink is created so templates that reference the 'current' directory get generated in the correct location.
Preparing the 2.4.1 release.
Merge branch 'master' of github.com:rubber/rubber
Bumped the version to 2.4.1.
Reworked the asset precompilation logic again to work in all cases.
Preparing the 2.4.2 release.