Recently libcurl was added as a required dependency, but it was not
updated for the debian install instructions

Tried to build on Fedora 21, complained about missing libcurl-devel.

Added instructions for Ubuntu 15.04
Added JACK2 support in Debian-based distros

OBS seems to require libx264-dev and libxinerama0-dev now, so I added them

missing 'install' on line 180

Add more details installation/compilation instructions for
Redhat-based distros, debian-based distros, Arch Linux, Gentoo, and
OpenSUSE distros

Fix incomplete Debian installation instructions, and separate out
instructions and package requirements that were specific to Debian-based
distros.  Most of the instructions in the file were previously specific
only to Debian.  Also added some brief instructions for an easy and
minimal FFmpeg installation.