Ensure that stdin is opened with mode 'rb'

This fixes the following error:

    $ echo foo bar | chardetect
    Traceback (most recent call last):
    ...
    TypeError: can't use a bytes pattern on a string-like object
Merge branch 'open-stdin-as-rb' of github.com:lpsinger/chardet into lpsinger-open-stdin-as-rb
Fix a Python 3 compatibility issue with lpsinger's PR.
Merge branch 'lpsinger-open-stdin-as-rb'