Download the samples binaries

[ncannasse]

In order to show that Heaps also runs on desktop, we should allow to download the sample binaries for OSX/Linux/Win

This involves preparing a precompiled HL package zip/tgz in which we inject the haxe compiled .hl file.

Not urgent for now, this can wait after the website has been finished

[markknol]

I now added that the samples are actually compiled while building the website (in Travis)
https://github.com/HeapsIO/heaps.io/blob/master/src/BuildSamples.hx

When HL build also works (at the moment it doesn't) we can make zips/packages from it.