Improves download table styling and adds Canary links

![example](https://cloud.githubusercontent.com/assets/1581276/4654761/7a9f97d6-54ba-11e4-9201-05386bdc7a0a.jpg)

- Removes server-side links to GitHub that required PHP files
- Adds client-side links to Canary packages in the same way that the Stable and Beta channels were added in the existing site
- Adds minor styling improvements for tables

Note the _Android (ARM + x86)_ and the _Tizen 3.0 Mobile (x86)_ links don’t work because none of these work on the existing site. Not sure if the naming conventions on these changed, but this fixes it for all the other links.