Update to 0.9.8:

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0.9.8
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* Issue #53: Fix NameErrors in `_vcs_split_rev_from_url`.

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0.9.7
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* Issue #49: Correct AttributeError on PyPy where a hashlib.HASH object does
  not have a `.name` attribute.
* Issue #34: Documentation now refers to bootstrap script in code repository
  referenced by bookmark.
* Add underscore-separated keys to environment markers (markerlib).

(wiz)