Remove yosys-abc from install-line

ABC is now a dependency for the yosys deb package, so having
yosys-abc on the install line is not necessary. Additionally,
the package is now called berkeley-abc.
Removed no longer supported Ubuntu version "saucy"

There are only Ubuntu packages for supported LTS versions in the PPA now.
Merge pull request #3 from rubund/master

Updated install instructions from Ubuntu PPA