test(Square): should have a value can set value

game-model file now exports a module that contains the classes to be
tested against.
test(Square): should be able to mark values
chore(comment): Input/Output for Square#markValue
test(Square): defensive programming on #markValue
chore(rename): consistent with naming conventions
refactor(Board): debugging w. good error messages

unit tests will test for the type of error being thrown and not the
error message itself. the error message may change to better address
new aspects of the project, but the nature of the test (RangeError) is
less likely to change.
fix(Board): testing for object response now works

`respondTo(<message>)` works if <message> is a function
to test for properties, use either `property` or `ownProperty`

-adds false positives to the test suite for extra measures against false
positives

-also clarifies test for length due to poor wording choice
test(Square): correct response testing for Square
refactor(Square): better error types and msg

- adds custom error type: NumberError to specify that the argument to
  Square must be a natural number

- updates test statement to indicate we are testing for RangeError and
  not just Error (reflect changes from previous commit)
chore(config): improve productivity with helpers

- adds underscore.js to package.json
test(Board): should have squares and nothing else

- tests for board composition, and clarifies test statement for (new) to
  be asserting that each Square should have a value of 0.
fix(Board): Square can be tested as a stub obj

Due to node's exporting mechanism, we have to define mock or stub
objects for assertions to work properly
test(Board): should initialize as a 3x3 board
refactor(Board): tests for new Board defined @ top
model(Board): data struct is made of Squares
refactor: all models declared at top-level

this was important because composition test was failing due to the fact
that it was comparing against a constructor of the same Class name, but
not of the same class.

Therefore, the stub object is removed.
refactor(Board): formatting 2d array
chore(comment) composition test should be omitted
refactor(Board): better wording for tests
Merge branch 'core-implement-Square' into develop

Conflicts:
	package.json
	test/unit/game-model-spec.coffee