Add the how to build md for pyocd
Add the how to build md for pyocd
Add blanks
modify syntax
modify syntax again
Update HOW_TO_BUILD.md
Update HOW_TO_BUILD.md
Update README.md
Update README.md
Update README.md
Close the usb interface in gdbserver stop

Explicitly close the usb interface to avoid any unwanted interface thread.
Merge pull request #41 from ECNU3D/pyocd-improvements

Update how to build binary package of pyocd