API change from 0.0.13->0.1.1

[alippai]

The httptools 1.0.0 release notes say that there should be no breaking change, but upgrading httptools from version 0.0.13 breaks uvicorn tests:

PR: encode/uvicorn#569
Test: https://travis-ci.org/encode/uvicorn/jobs/647886597

[elprans]

You should NOT import anything from httptools.parser directly (that is private API). The only public API is whatever is available under httptools directly, including the exception classes.

[elprans]

#53 restores the behavior of 0.0.13, but please fix your code to not import anything from httptools submodules, we will make them private in a future release.