Bruker2nifti

+ Thanks to [gdevenyi](https://github.com/gdevenyi) for raising issues regarding the flags inconsistencies between the GUI and CLI. See #58 and 59 .
+ Black auto-formatter introduced.

+ Integrate `offset_correction`.
+ added `sample upside down` option
+ integrated `frame body as frame head`
+ abandoned nose testing for pytest
+ add radio button for `sample_upside_down`
+ new folder structure `cli` and `gui`
+ bug fixed issues 41 with latest release

Following issues 34 and 35: few bugs fixed to work in the windows environment.

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+ Python 3 and back compatible with Python 2.7
+ Travis-CI for continuous integration
+ Help reference in the Graphical User Interface, and upgraded GUI
+ Coverage testing - in progress - 71%
+ BUGS corrected from the [previous version](https://github.com/SebastianoF/bruker2nifti/releases/tag/v1.0.0) (v1.0.0): removed blind parameter `-axis_direction` in the parser parameters list. Removed wrong parameter update in the parser bruker2nifti.

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+ Python 2.7 only
+ Released on pypi (wheels)
+ Graphical user interface and GUI launcher creator
+ Command line utilities
+ Nosetests coverage 65%