v0.9.0

Fixed a small bug in the qsub command and added the --tag option to overwrite the resource tags defined in samples.yml and pipeline.yml files.
The new --tag option must be used as follows from the command line:

pipengine run -p awesome_pipeline.yml -f my_samples.yml -q batch_queue -s mapping --tag index=/path/to/new/index gtf=/path/to/new/gtf