Bundler integrated Capistrano provider

Executes bundle install during deployment without surrounding bundler
environment. After that, cap deploy is run normally.
Fix Elastic Beanstalk S3 bucket configuration
Merge pull request #85 from dlackty/patch-1

Fix Elastic Beanstalk S3 bucket configuration
Install only gems from heaven and deployment groups
Updates the flowdock gem to the latest. Enables threaded notifications.

flowdock 0.5.0 adds support for the message_thread parameter added in #83
Merge pull request #87 from kiratalent/update-flowdock-gem

Updates the flowdock gem to the latest. Enables threaded notifications.
Merge pull request #86 from flowdock/bundler-capistrano

Bundler enabled Capistrano provider
use octokit 3.4.0
don't hardcode the octokit version in tests
upgrade warden-github to handle gravatar url deprecation
Merge pull request #89 from ZeroFucks/upgrade-gems

Upgrade gems
change heroku deploy button to svg version
Merge pull request #90 from bgentry/heroku-button-sv

change heroku deploy button to svg version
Read deployment task name from correct place

Fixes #91.
Merge pull request #92 from flowdock/task-data

Read deployment task name from correct place
Add BRANCH env to bundler_capistrano deploy
Validate ref in capistrano deployments
Provide BRANCH env to capistrano through child processes's env.
Move ref validation to default_provider
Merge pull request #93 from flowdock/bundler-capistrano-cap3-support

Cap3 support for bundler_capistrano