Bump travis-build once and for all

It's now an API!
Pull build script from API
runner: don't merge in config data

The Script class merges this in already, so no need doing it twice.
script: send a user-agent to the script API
script: add a timeout
remove leftover travis-build require
script: JSON encode the payload
api: set the Accept header

This allows us to more flexibly change what the API does by switching on
the Accept header in the future.
Merge remote-tracking branch 'origin/master' into hh-build-api
script: fix typo 'etch_hosts' -> 'etc_hosts'
script: use travis-build locally if the API config isn't set

This allows us to deploy the code to all workers and then gradually
switch over to using the API.
reenable lang mappings in Docker
print out lang mappings during Docker startup
convert lang to sym

lang mappings are sym => string
Revert "convert lang to sym"

unneeded as hashr does this for us

This reverts commit 00d28e01dd5b89abdd49c2bbea48ff1aceec2e08.
Merge branch 'master' into hh-build-api

Conflicts:
	Gemfile.lock
correct the docker image selection logic
Merge branch 'master' into hh-build-api
use the Docker way of setting the cpuset for the container
Merge branch 'master' into hh-build-api