v0.2.0, 2015-01-18
 * introduce generalized range objects (affecting most functions, yet in a backwards compatible way)
 * fix wrong documentation for function sort_by_start
 * add function difference_one_multi
 * add keyword argument do_normalize to functions filter_equal, filter_overlap, filer_contained
 * minor improvements on documentation
v0.1.3, 2014-11-07 -- Fix an edge case in normalize_multi
v0.1.2, 2014-07-25 -- Mostly improved documentation
v0.1.0, 2014-07-24 -- Initial release

