Small bugfixes and manifest_version 2.0 compatiblity

I fixed a typo and a bug in desktop notifications that was caused by a bug in Chrome. 

Also, I fixed the manifest version to 2.0 and made relevant changes. The background page is now autogenerated and inline javascript calls in HTML have been converted to event handlers.

sanitz: I'd really appreciate it if you took the time to update the version of the plugin found in Chrome Store.