Update ECOS.jl information

@jfsantos

There were two independently started versions of the Julia ECOS interface. The one by @jfsantos has actually been completed by myself and integrated into the Julia optimization interface. It also has support for automatically downloading and building on Linux and OSX, and we're about to add binary download support for Windows. Hopefully it'll be one of the easiest ways for people to download and try ECOS.