Add Version section to README.md

Easier to track which is the last version of the plugin.
Fix indent in README example
Merge pull request #15 from jfgodoy/master

function bounce now receive an object of parameters
Remove extra spaces
Rework bounce() options object handling
Update README

Passing arguments has changed, now bounce() accepts both separated arguments or
an object.
Separated arguments is marked as deprecated and should *NOT* be used anymore.
Add ending callback feature

When using bounce(options, callback), you can now use an optionnal callback that
will be executed when the animation end.
Rework fully README