Added STM32 code, and fixes in Readme.MD

[hugogarrix]

Hi, thanks for your contribution! Take a minute to tell us more about your changes:

Description

• Added STM32 code
• Made the needed changes to the Readme.MD
• Fixed a few typo's in the Readme.MD
• Added a NOTE about the exhibited stability issues of the Arduino DUE, and support of it.
• Added a Pull request template, to make it more clear for people what they need to do, and to make it more easy for us to check them. (Looks the same like the one Im now using.

Motivation and Context

This changes "upgrade" the headset. The STM32 board is smaller, and cheaper than the Arduino DUE, and next to that, it resolves about 95% of the issues we had with OSVR. The code of the STM32 board is a lot more stabel then the Arduino DUE's code.

How Has This Been Tested?

All the code has been tested by Justin, Haagsch and me.

Those changes also effects the Arduino Libraries. All information about this can be found in the new Documentation, that has been written by Justin.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.