Skip cgroups install on travis-ci

Not supported? Installing cgroup-bin results in:

Setting up libcgroup1 (0.37.1-1ubuntu10.1) ...
Setting up cgroup-bin (0.37.1-1ubuntu10.1) ...
start: Job failed to start
invoke-rc.d: initscript cgconfig, action "start" failed.
dpkg: error processing cgroup-bin (--configure):
 subprocess installed post-installation script returned error exit status 1
Processing triggers for libc-bin ...
ldconfig deferred processing now taking place
Errors were encountered while processing:
 cgroup-bin
E: Sub-process /usr/bin/dpkg returned an error code (1)

Added install configuration ISOLATE_CGROUPS:
- not installing skips apt-get install cgroup-bin
- puts cgroups: false into the isolate.yml
Use control groups with new judge, refactoring

- Isolate service uses control groups by default
- Refactor compile code to language model
- Meta hash value conversion to float and integers as appropriate
pass all specs with old judge - before starting to link new judge up