Add mockjax for mocking requests/responses

and a couple more tests
On branch testing
Changes to be committed:
  (use "git reset HEAD <file>..." to unstage)

	modified:   README.md
	modified:   build/hgrid.js
	modified:   src/hgrid.js
	new file:   tests/jquery.mockjax.js
	modified:   tests/test-hgrid.html
	modified:   tests/test-hgrid.js