Strip-hints

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Added the options ``--outfile`` and ``--inplace``, along with ``--help``.

Bug fixes:

* Fixed a bug where comments in function return hints that contain both newlines
and comments cause syntax error when the ``--strip-nl`` option is used.

* Fixed a bug in multiline annotated expressions with comments on the lines.

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Added the options ``--strip-nl`` and ``--no-equal-move``. Fixing annotated
assignments with newlines in type hints by moving the line with ``=`` was
added.

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Added a new Python interface function ``strip_string_to_string`` which works
just the same as ``strip_file_to_string`` except it takes a code string
argument instead of a file name.

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Added an `importlib` stripper for strip-on-import for Python 3.

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Fixed strip-on-import for Python 2.

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Fixed a unicode decoding bug when running under Python 2 on a file containing a
unicode string.