------------------ - create TextPositionSelector .real_start and .real_end - create TextPositionSet.add_margin
0.4.1
------------------ - TextPositionSetFactory will accept list of strings - subtracting more than start value is no longer IndexError, but more than end value is - TextSequence quoting from empty string doesn't start with None
0.4.0
------------------
- TextPositionSet can output a TextSequence - create TextSequence addition method
0.3.3
------------------
- fix bug: leading whitespace when selecting from prefix
0.3.2
------------------
- fix bug where adding selectors converted them to parent class - add TextSelectionError exception
0.3.1
------------------
- add left and right margin parameters to TextPositionSelector.as_quote_selector - as_quotes method for TextSelectorSet - enable adding int to TextSelectorSet - fix class name in repr for TextSelectorSet