Cygwin support added. Tests added. Settings now reloaded on each PerlTidy run.

* User setting "perltidy_options_take_precedence" added. If set to "true",
  which is the default, options from user setting "perltidy_options" will
  take precedence over options found in perltidyrc files.
* Added automatic detection of perltidy in default installations
  of Strawberry Perl/ActivePerl/Cygwin on Windows.
* Settings are now reloaded on each run of PerlTidy.
* Now using sublime.platform() instead of os.name for getting platform
  name.
* Now catching EnvironmentError exceptions instead of OSError in
  tidy_region(). This will also catch IOError exceptions, which previously
  were not catched at all.
* Added messages to be displayed by Package Control on installation
  and upgrades in "messages/". Added "messages.json" to link the messages.
* Removed accessors: get_perltidy_options(), get_perltidy_rc_paths().
* Refactored most of the code and moved it to perltidy/helpers.py, so we can
  test it, without mocking too much.
* Documentation improved.
Bumped plugin version number. Latest version does not appear in package list.
Documentation updated.
Merge origin/master into devel.
Added option "perltidy_use_temporary_files" for forcing temporary file usage.