Improve installation & instructions

[suan]

• symlink executable to /usr/local/bin/prax in installation
• add instructions to recommend cloning to a proper location such as /opt, and how to autostart the server by placing prax start into .profile or .bash_profile (would've added this to installation too but alas debian has no standard way to autostart commands run as a user, except for modifying these login files directly. Actually, another way would be to have the init script scan all /home directories for .prax/, and whichever has those, start prax under that user. Maybe later)

With this in place, all that's left to get to an actual package is using something like fpm to put all the files in /opt and run prax install after the package has been installed.

[ysbaddaden]

Thanks for the documentation!

[ysbaddaden]

Now I'm eager to see what fpm would provide :)