Fix docs to use event model for page changes

Updated the code and doc to use event instead of callback onPageChange
First commit, be gentle :-)

I moved this commit from https://github.com/openseadragon/openseadragon.github.com/pull/9
Update Scalebar plugin URL
Merge pull request #56 from avandecreme/patch-2

Update Scalebar plugin URL
Syntax and suggested updates
Merge pull request #55 from macarthy/patch-1

Fix docs to use event model for page changes
Minor text fix
adds sourcemapurl to main bower.json
Merge pull request #57 from mejackreed/add-sourcemap-url

adds sourcemapurl to main bower.json
Updated logo and tagline
Mentioned Bower
Mentioned Gitter
Merge pull request #58 from openseadragon/info

Front page additions
Create ui-customize-tooltips.html