Tag class added

Created a class for tags.
Refactoring

Encapsulated some setup code in a few classes in order to bring them
more in line with the structure of the rest of the classes.
Refactoring

Reworded a test step because not every spec run from feature files
is a unit spec.
Code coverage updates

Filtered out test files from the code coverage results and changed the
rake task that runs the full test suite to automatically clear the old
code coverage results first.
History update

Updating gem history in preparation for v1.2.0 release.
Version bump

Gem version bumped for v1.2.0 release.