Add pypixelbuf as a dep

Author: tannewt

setup.py

@@ -30,7 +30,7 @@
     # Author details
     author="Adafruit Industries & Damien P. George",
     author_email="[email protected]",
-    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