stmhal: Add pyb.wfi() function (calls __WFI).
stmhal: Improved usart module a bit.
stmhal: Work around crazy bug in USB CDC.

Packets of 64 bytes length are not send to the host until the following
packet is sent.  Fixed by never sending packets of 64 bytes length.
tools: Improve timout/reading of pyboard.py.
Don't allow both ENDIANNESSes to be set

See discussion on https://github.com/micropython/micropython/commit/2da81fa80c4cd965f05ad237d81d9764322fde20

Explicitly set `MP_ENDIANNESS_LITTLE` because that's the #define that is used in code elsewhere.
Make pip-micropython more portable

Replace /tmp with a $TMPDIR variable
Replace multiple occurrences of /tmp/pip-micropy-venv with a $TMPVENV variable
Replace ~ with $HOME
Add Travis CI support.
Merge branch 'master' of github.com:micropython/micropython
Merge branch 'master' of github.com:micropython/micropython
Make USE_COMPUTED_GOTO a config option in mpconfig.h.

Disabled by default.  Enabled in unix port.
Merge pull request #484 from aitjcize/travis

Add Travis CI support.
Update README to include build status from Travis CI.
Merge branch 'master' of github.com:micropython/micropython
Fix README build status image.
Merge pull request #480 from lurch/patch-2

Make pip-micropython more portable
Merge pull request #479 from lurch/patch-1

Don't allow both ENDIANNESSes to be set
travis: Change to tests directory before running.
pip-micropython: revert $HOME back to ~
Merge pull request #485 from lurch/patch-1

pip-micropython: revert $HOME back to ~
py: Implement __delitem__ method for classes.