Switch to build from circuitpython 2.x branch mpy-cross

Author: tdicola

.travis.yml

@@ -44,7 +44,7 @@ deploy:
 before_install:
 - sudo apt-get -yqq update
 - sudo apt-get install -y build-essential git python python-pip
-- git clone https://github.com/adafruit/micropython.git
+- git clone https://github.com/adafruit/micropython.git -b 2.x
 - make -C micropython/mpy-cross
 - export PATH=$PATH:$PWD/micropython/mpy-cross/
 - sudo pip install shyaml