Fix behaviour when DummyAttrs remain in query.
Fix missing EOL.
Remove DummyAttr from HEK walker.
Add tests for HEK.
Fix downloader deadlock.
Add a word about Anaconda.
Add word about multiple Python envs.
No longer leak fds.
Fix bug in downloader.
Improve test.

Add timeout to download test.
Code style change.
Remove test code.
Improve download test suite.
Fix Windows file naming.

Closes #331.
Add get_system_filename_slugify
Merge pull request #493 from segfaulthunter/vsofix

Fix VSO behaviour wrt DummyAttr
Merge pull request #499 from segfaulthunter/fdleak

No longer leak fds.
Merge pull request #497 from segfaulthunter/dwfix2

Fix misc downloader bugs
Merge pull request #498 from segfaulthunter/installdoc

Anaconda in install docs