Remove hack to encode __all__ as ascii (#178)

Previously the code included:

    from __future__ import unicode_literals

But with that gone in the current version, it makes no sense to
mess with the contents of __all__ at all.

Author: bz2

prometheus_client/__init__.py

@@ -6,8 +6,6 @@
 from . import platform_collector
 
 __all__ = ['Counter', 'Gauge', 'Summary', 'Histogram']
-# http://stackoverflow.com/questions/19913653/no-unicode-in-all-for-a-packages-init
-__all__ = [n.encode('ascii') for n in __all__]
 
 CollectorRegistry = core.CollectorRegistry
 REGISTRY = core.REGISTRY