Merge tag '0.8.0' into develop

bug fixes and preprocessing
Added option --skip-preprocess
Close hocr files as they're used to stop running out of file handles
cleaned up an old hocr overlay function that was not being called
added scan_interval option to increase time when watching a directory
Fixed some formatting in doc
Fixed some tests and coverage
0.8.1 bump
Updated exe
Merge branch 'release/0.8.1'