Updated for 2.0.0.  Relates to gh-133
Use %w and single quotes
Quote log output of var info
Don't get output_file if it's empty
Log which label is being created
Added tag to remove #result; doesn't seem to be used
Updated YAML formatter to output all problems.

Previously, it was only outputting either the first or the last problem
for a file, but not all problems for a file.  Relates to gh-131.
Added rake task to use YAML
YAML needs to be Yaml.  Relates to gh-131
CLI now takes an optional Configuration object.

This allows RakeTask to create its own configuration (including file
sets) and pass it along.

Also, RakeTask now assumes that if #config_file is given, you want to
you use the file_sets defined in that config file, thus file_sets
defined in the rake task will be ignored.  If you want to define file
sets in your rake task, don't use #config_file.

Also, init Reporter formats to 'text' if somehow, none were given.

Closes gh-129.