core: add output/detail methods to Ui, prefix with arrows
core: colorize VM output for each VM in a command
core: align text and make sure its all lined up with prefixes
providers/virtualbox: many `detail` level output
providers/virtualbox: more detailed output
Fix tests for new UI methods
core: convert more output to `output` method
core: Ui color should be red on errors, yellow on warnings
core: extensive tests for Vagrant::UI classes
core: make output white for now
website/www: blog posts on Vagrant stability
Merge pull request #2857 from mitchellh/f-ui-revamp

UI revamp
core: only bold when output is part of a machine
core: use cleaner UI abstractions