Include LANG in the environment variables

Without this some build scripts in Python 3 will give

Traceback (most recent call last):
  File "setup.py", line 12, in <module>
    long_description=open('README.rst').read(),
  File "/Users/aaronmeurer/anaconda/envs/_build/lib/python3.3/encodings/ascii.py", line 26, in decode
    return codecs.ascii_decode(input, self.errors)[0]
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc2 in position 2326: ordinal not in range(128)