Set execute bit

Signed-off-by: Andy Grover <agrover@redhat.com>
Add mention of File::Slurp dependency

And what it's packaged as on RH and Debian.

Signed-off-by: Andy Grover <agrover@redhat.com>
Merge pull request #1 from agrover/for_tbayly

Some small fixes that might help people getting started using santop