Modified execute code to handle srun on cluster, exclude matlab commands, and allow for a custom queue to be specified via the ENV variable PIPELINE_QUEUE.
Fixed the issue with the way $PIPELINE_QUEUE was handled by the code.  Will successfully run on defq if $PIPELINE_QUEUE is not previously set; will successfully run on specified queue otherwise.
Merge branch 'master' of https://github.com/jamesjcook/pipeline_utilities

Pulled from github.