added a persistence map module to eitwaveutils.py (c.f. Barbara Thompson)
added a call to map_persistence. Persistence maps are now returned as well as other products.
added an attempt at re-ravelling in eitwaveutils.py
merged latest changes from upstream/master
bug fix for map_unravel within eitwaveutils. Parameter names taken by util.map_hpc_to_hg_rotate have changed. Edits to data_hough_detect - added check on whether specified data directory exists. If not, then it is created. Added check when reading from feed_directory. Only files ending with the extension specified in source_data (e.g. .jp2) are read.
Merge pull request #29 from aringlis/master

Added persistence map module to eitwaveutils