Remove suppression of gcc warnings in CFLAGS adafruit#336

CFLAGS is only -Wall now.  -Werror has been removed to the build will no longer fail on warnings.  Therefore, there is no need to suppress certain warnings.

Author: pdp7

setup.py

@@ -21,7 +21,7 @@
 else:
     kernel41 = None
 
-CFLAGS = ['-Wall', '-Wextra', '-Wno-missing-field-initializers', '-Wno-strict-aliasing' ]
+CFLAGS = ['-Wall']
 
 classifiers = ['Development Status :: 3 - Alpha',
                'Operating System :: POSIX :: Linux',