Some relays are unreliable, but we still want the tests to check
the different types of relays.

Part of 28863.

And move a comment.

Part of 28863.

Part of 28863.

But maintain compatibility with older stem versions.

Part of 28863.

Comment-only change.

Part of 28863.

Part of 28863.

This change makes it easier to run the travis tests locally.

Part of 28863.

Part of 32632 and 28863.

Part of 28863.

Part of 28863.

Part of 28863.

Part of 28863.

Use Xenial for pypy.

Part of 32632 and 28863.

Use Ubuntu Bionic and macOS 10.14.

Install Homebrew python@2 in macOS
macOS needs pip(2) to install fallback scripts dependencies.

Part of 32632 and 28863.

* Restrict the valid True and False bool values
* use default for unset env var, and (not default) for empty set env var

Closes 31305.

Part of 31305.

Also add a requirements.txt

Initial implementation of #28979.

Tested with:
TOR_FB_ONIONOO_LIMIT=200 ./updateFallbackDirs.py

Part of 29100.

Tested with:
$ TOR_FB_MAX_FALLBACK_COUNT=10 ./updateFallbackDirs.py check_existing
$ TOR_FB_MODE=check_existing TOR_FB_MAX_FALLBACK_COUNT=10 ./updateFallbackDirs.py

Part of 29100.

Tested using:
$ TOR_FB_MAX_FALLBACK_COUNT=10 ./updateFallbackDirs.py

Part of #29100.

And remove a duplicate "import re".

Part of 29100.

Closes 28986.
Patch by starlight, edited by teor.

Part of 29100.

Part of 29100, but these files are created by the scripts in 28794.

Closes 30948.

Closes 30947.

Closes 29100.

Tested with:
TOR_FB_ONIONOO_LIMIT=200 ./updateFallbackDirs.py

Part of 29100.

Tested with:
$ TOR_FB_MAX_FALLBACK_COUNT=10 ./updateFallbackDirs.py check_existing
$ TOR_FB_MODE=check_existing TOR_FB_MAX_FALLBACK_COUNT=10 ./updateFallbackDirs.py

Part of 29100.

Tested using:
$ TOR_FB_MAX_FALLBACK_COUNT=10 ./updateFallbackDirs.py

Part of #29100.

And remove a duplicate "import re".

Part of 29100.

Part of 29103.

Remove the parts of the LICENSE that only apply to external source code
distributed with Tor, and edit the header.

Rewrite the README with specific information about the Tor Fallback Scripts.

Closes 29103.