Removed assert: true when installing dpl gem
Merge branch 'master' into no_deploy_assert

Conflicts:
	lib/travis/build/script/addons/deploy.rb
	spec/script/addons/deploy_spec.rb
Added allow_failure option
Removed allow_failure from config
Made allow_failure an accessor
Merge pull request #125 from Aaron1011/no_deploy_assert

Conditionally allow deployment commands to fail

This'll help us implement travis-ci/travis-ci#1412 in a configurable way.