Fix incorrect value of captured property for en passant captures

When an en passant capture was made the returned move object did
not have its captured property set to 'p'. The make move test cases
had to be modified a little to test for captured property as well.
Remove redundant conditional check
Using Mocha/Chai for js testing.
Merge pull request #23 from imor/epCaptureFix

Fix incorrect value of captured property for en passant captures
Merge branch 'mocha-tests' of https://github.com/linrock/chess.js into linrock-mocha-tests

Conflicts:
	tests/tests.js
Update TODO and contributors list.
Fix .pgn() docs in README
Merge pull request #26 from linrock/fix-docs

Fix .pgn() docs in README
Fix issue #27.

Removed trailing comma.