v0.0.3 -- Added a callback and custom class

- Added possibility to specify a class for <tr>s created by updateFromObj()
- Added a callback function to execute once data is loaded in updateFromObj()
- Also corrected a bug in constructor : the <th>s in the <thead> were written after the <tr></tr>, messing the display in some cases. Not sure i did it the best way possible, though...