Carried over from master
No need to use get_window_size; also handles situations where window size is variable.
Cross-validation of windowed beds. FOR SOME REASON doesn't throw out anything, needs testing!
Quickfix: filters out values that are zero. Doesn't yet filter values that are too close.
Removed deprecated method enrichment.view (view-bed).
Removed deprecated flag --both-strands
Very shallow help entry for filter-windows.
More correct way to handle an OSError exception.
Added flag --hard, renamed flag -o to --output
Draft working version of cross-filter.

(previously called filter-windows).
Uses the three-sigma rule rather than a statistical test.
Merge branch 'development'