Another bug fix

* Whole word guesses of random casing (e.g. "aNIMaL") were regarded as an invalid guess regardless of whether it was correct
* Updated code to downcase a whole word entry before checking validity
* Added rspec tests to help work towards fixing bug (done)
* Applied change in cucumber tests to fix a failing test caused by previous changes to code.
A set of small changes

* Reversed a change in word generator (was changed for testing purposes)
* Updated validator to treat white space the same as entering nothing for a guess
* Added a new game button to webapp
* Added some CSS styling to new button and existing button, plus some other slight visual changes.