changed table header cursor to a mouse pointer

modified backgrid.css to change the mouse pointer to a cursor so that
the user knows that they can click on it to sort.
Merge pull request #29 from jonaldomo/master

change table header mouse cursor
Remove note on opera, it's working fine now that contenteditable is not longer used
Fix #30
List out the core editor classes explicitly in api doc
Transpose CSS property and value and really fix PR #29 shamelessly
Generate extension directory structure properly
Add mixpanel
Merge branch 'master' into 0.2.0-wip
Fix issue #28
Direct questions to Github instead
Fix #36 row element not inserted to body if body has no rows when calling insertRow
Remove console.log
Fix #26 use document fragment to speed up row and cell rendering
Clean up unnessary selfs to save some bytes
Clean up unnessary self
Clean up unnessary self and fix doc
Improve test case for Body#insertRow and code clean up
Fix backbone-pageable issue 34
Fix #40 custom header, body, footer and row as grid constructor options