Isort

- Fixed 546: Can't select y/n/c after latest update
- Fixed 545: Incorrectly moves __future__ imports above encoding comments

- Fixed 428: Check only modifies sorting
- Fixed 540: Not correctly identifying stdlib modules

- Added `--virtual-env` switch command line option
- Added --enforce-whitespace option to go along with --check-only for more exact checks (issue 423)
- Fixed imports with a tailing '\' and no space in-between getting removed (issue 425)
- Fixed issue 299: long lines occasionally not wrapped
- Fixed issue 432: No longer add import inside class when class starts at top of file after encoding comment
- Fixed issue 440: Added missing `--use-parentheses` option to command line tool and documentation
- Fixed issue 496: import* imports now get successfully identified and reformatted instead of deleted
- Fixed issue 491: Non ending parentheses withing single line comments no longer cause formatting issues
- Fixed issue 471: Imports that wrap the maximum line length and contain comments on the last line are no longer rendered incorrectly
- Fixed issue 436: Force sort within section no longer rearranges comments
- Fixed issue 473: Force_to_top and force_sort_within_sections now work together
- Fixed issue 484 & 472: Consistent output with imports of same spelling but different case
- Fixed issue 433: No longer incorrectly add an extra new-line when comment between imports and function definition
- Fixed issue 419: Path specification for skipped paths is not Unix/Windows inter-operable.
Breaking Changes:
- Fixed issue 511: All command line options with an underscore, have had the underscore replaced with a dash for consistency. This effects: multi-line, add-import, remove-import, force-adds, --force-single-line-imports, and length-sort.
- Replaced the `--enforce-whitespace` option with `--ignore-whitespace` to restore original behavior of strict whitespace by default

- Fixed an issue that caused modules to inccorectly be matched as thirdparty when they simply had `src` in the leading path, even if they weren't withing $VIRTUALENV/src 414

- Fixed an issue that caused module that contained functions before doc strings, to incorrectly place imports
- Fixed regression in how `force_alphabetical_sort` was being interpretted (issue 409)
- Fixed stray print statement printing skipped files (issue 411)
- Added option for forcing imports into a single bucket: `no_sections`
- Added option for new lines between import types (from, straight): `lines_between_sections`

- Fixed a large number of priority bugs - bug fix only release