Add .gitattributes to prevent test/lint failures in some envs

[johncaruso]

After an initial clone, due to my global git settings, npm install showed failing tests that were all related to a comparisons with line endings of \n failing.

Adding a .gitattributes allows git glone in windows to preserve the line endings correctly allowing the unit tests to pass - regardless of a users global git config.

[adrianheine]

Thanks!