make sure lab-grapher is in the right place
split out the preparation tasks from 'clean-finish'

this way they can be called separately
additionally make test has more dependencies so the following
sequence of commands will work:
bundle install;npm install;make prepare-submodules;make test
use travis_retry and prepare-submodules

there should be no reason to run 'make clean' because
travis always starts clean. However our 'make clean' 
does more than delete build products, it also prepares
for building. This preparation can now be done
independently with prepare-submodules.