Revert "Remove Typesafe copyright line pending clarification."

This reverts commit 7acf80a9824cf6aaa6a0a672e4054340c7f9039e,
as the copyright attribution for Typesafe was clarified.
Clarify it's the standard 3-clause BSD.
Move installation instructions to download page.

So that they are 0 clicks away from the actual download
that they pertain to. Reformulated them to be a bit more compact,
so they don't crowd the page.
Merge pull request #129 from adriaanm/install-on-dlpage

Install on dlpage