Upgraded to rspec3
Added a spec_helper.rb file
Updated specs to use the new rspec expect syntax
Converted from using instance variables to let statements
Renamed nickel_spec to parse_spec
Reworded the descriptions in parse spec to be more objective and rspec-like
Decided to move parse_spec to nickel_spec

Only had one test anyway
Updated requires in nickel_spec
Changed nickel_spec to pass a module (rather than a string) to the root describe
Ported zdate_test to rspec
Ported ztime test to rspec
Added occurrence#==

Need that for testing nlp, which produces occurrences, and I need to be
able to test if those occurrences are equal to one-another
Added require statements to files, so they can be loaded independently
Made travis run all specs individually, then as an entire suite with coveralls