Fix issues: checking equality on documents with a range key should take the range value into account, correct behaviour of documents when used as keys in a Hash
Better implementation of Document == which ignores range if the object being compared does not respond to range_value
Change tests to be more descriptive of what is being tested, as suggested by luxx
Change hash method so that it doesn't unnecessarily create an array during hash computation
Simplify logic in Dynamoid::Document's equality check
DRY up document tests
Merge pull request #105 from mpatric/master

Fix equality check when documents have a range key, and correct behaviour when documents are used as hash keys