Update .travis.yml by adding a submodule.
Drop the symlink.  Travis can't submodule.
Update submodule URL for travis.
Drop symlink again.
Update .travis.yml file
update python ebuilds with proper variable usage
dev-python/pycallgraph: simplify dependency strings
dev-python/pycallgraph: update Manifest
app-emulation/singularity: remove from overlay

singularity is no longer maintained or desired and is being removed from
this overlay.
Merge branch 'master' into www-servers/tornado
www-servers/tornado: bump version to 4.0.1