Pass the current element to before and after hooks

This allows for per-element configuration where there are multiple share buttons on the same page.
Update readme with dynamic `before` hook example
Merge pull request #72 from seanlinsley/pass-current-element

Pass the current element to before and after hooks
Build compiled versions
Automatically URL-encode the share link

This way the developer can use a query string on their URL without
having to think to encode it first.
code style update
only encode the query string if it isn't already encoded
`cake build`