Directing users to get guake

**Problem**: The "How do I get Guake" section of website should make it clear that github tarballs are _useful for inspecting source, but not building_ from.
**Result**: Information path is guake-project.org -> github -> readthedocks
**Suggestion**: Clarify about tarballs on guake-project.org. Add a direct link to the "install-from-source" section of readthedocs

Longer descripton with links-
---

1.
http://guake-project.org/
under "How can I get Guake?" states
"Guake is packaged by a large number of distributions, among which are Fedora, Debian, Ubuntu and ArchLinux, so please check your repo. _Source **tarballs are available; see the Release Page**_" (links to https://github.com/Guake/guake/releases)

2.
https://github.com/Guake/guake#note-when-compiling-from-source
states **"Do NOT use the Tarball packages** automatically generated by GitHub on the Release pages. They won't work because one of the main components of Guake build system, PBR, requires the full Git history to be available when building from source"

3.
Github then refers to the following link for installing from source
https://guake.readthedocs.io/en/latest/user/installing.html#install-from-source

So my issue is not with the bold section of point _2_, but just that point _1_ is specifically about how do I **Get** Guake, so its a bit mean to point the would-be user at a dead end; It's a wonderful program and people should be able to get it as fast an easily as possible :) Thanks for developing it, I use it every day for the past 2 years now.