Major cleanup and update of the front page

[lihaoyi]

The front page really needed a cleanup. We can argue over the specifics, but this should prettify it and bring it up to date and make it a lot more welcoming to someone new to ScalaJS =)

• Added uPickle and autowire to the list of libraries
• Added @sjrd's talk to the list of presentations
• Added the ray-tracer and papa-carlo-incremental-parser-demo to the list of sites using ScalaJS
• Converted list of libraries etc. from HTML lists to sub-headers, added SBT snippet for each one.
• Moved the 0.5.2 announcement to the bottom of the page, together with a list of other version announcements. For someone who just arrives at the site and wants to use ScalaJS, the version-release-announcement is probably of no interest
• Moved IMPORTANT NOTICE to the bottom of the page; I don't think it's that important that we should shove it in the face of everyone who comes to look at the site

[sjrd]

OK, except this:

Moved IMPORTANT NOTICE to the bottom of the page; I don't think it's that important that we should shove it in the face of everyone who comes to look at the site

Actually it is. The Scala macros project did not make clear enough that it was experimental, and changes became very hard to introduce. It's a courtesy of ours to Typesafe to make it very clear that it is not supported by them.

That said, given that Scala.js has stabilized quite a bit lately, we can move it down a bit. Probably at the end of the section of Getting Started. (Before the Noteworthy features title).

Speaking of the Getting Started section, it would be cool to have two big buttons "Get started with the Tutorial" and "Try it out in the browser" in that section, rather than text. Especially now that the button for the latest version announcement is not there anymore.
I believe this is what people want to find most: how to try it, isn't it?

[lihaoyi]

Both suggestions sound reasonable, will make the changes

[lihaoyi]

@sjrd updated it

[lihaoyi]

[sjrd]

LGTM Thanks!