Single Line install for Geth

[alexvandesande]

We need a single line (or the closest possible) for the latest stable geth binary on Linux and Mac.

Currently, the best we have is:

ruby -e "$(curl -fsSL https://raw.githubusercontent.com/cubedro/frontier.ethereum.org/master/bin/install.rb)"

Which is bad because it uses ruby, which isn't default in most systems and the main url could be made much better (github cubedro??)

[karalabe]

To add to it, "Linux" above is Ubuntu in reality. If will fail miserably on anything else (or at least not apt-get based... like 2/3 Linux distributions)