Add pypixelbuf as a dep

Author: tannewt

setup.py

@@ -30,7 +30,7 @@
  # Author details
  author="Adafruit Industries & Damien P. George",
  author_email="circuitpython@adafruit.com",
- install_requires=["Adafruit-Blinka"],
+ install_requires=["Adafruit-Blinka", "adafruit-circuitpython-pypixelbuf>=2.0.0"],
  # Choose your license
  license="MIT",
  # See https://pypi.python.org/pypi?%3Aaction=list_classifiers