This just fixes a broken link by deleteing it.

I'm assuming Jinja 1 docs. aren't readily available anymore.
I looked for a git tag for version 1 as an alternative target,
but didn't see that either.

* Added new maintenance branch format to Travis

The maintenance branch format appeared to change from
`[version]-maintenance` to `[version].x` in the recent months, and
this broke Travis CI builds made to those branches. Because they
no longer meet the branch regex, the pull requests builds against
these branches were no longer being run.

This ads the regex for any branch which ends in `.x`, which should
catch the new pattern for maintenance branches.

* Use the branch regex from werkzeug

This is more specific to only catch version number branches.

* Sync with master

Apparently the build configuration for this branch is very old and doesn't match master at all.

fixes pallets#242, deletes link to Jinja 1 docs.

This commit updates the examples to conform to Python 3 instead
of Python 2, as Python 3 is more acceptable these days.

docs: Python3-ize the examples

Remind not to put block in if statements in doc

adds documentation on use of python methods in expressions

In Python 3.7, importing ABCs directly from the `collections` module shows a
warning (and in Python 3.8 it will stop working) - see
python/cpython@c66f9f8

This fixes various DeprecationWarnings such as those:

```
.../jinja2/utils.py:485: DeprecationWarning: Using or importing the ABCs from 'collections' instead of from 'collections.abc' is deprecated, and in 3.8 it will stop working
  from collections import MutableMapping

.../jinja2/runtime.py:318: DeprecationWarning: Using or importing the ABCs from 'collections' instead of from 'collections.abc' is deprecated, and in 3.8 it will stop working
  from collections import Mapping
```

…ollections-warning-fix

Backport python3.7 collections warning fix

Azure has Python 2.7.15 and Python 3.5.5, which can't parse async code.
Later patch versions can parse it fine, so this can be removed if
Azure updates.

Since around pytest 3.6 it's been possible to register custom
markers, and since version 4.5.0 pytest warns about any which
are not registered. Register a list of such markers, extracted
from those warnings, so they don't clutter the test output.

Fix pytest unknown mark warnings

Fix memory usage bug in Python 2 by using correct version of range

Add Links section to README

modernize docs, 2.9.x branch

Fix issue pallets#1050: fix a crash in TracebackFrameProxy.set_next() on
Python 3.7 and newer, when Python is build in debug mode.

Since Python 3.7, traceback.tb_next field can be modified: ctypes is
no longer needed.

Fix TracebackFrameProxy.set_next() on Python 3.7

2.10.3+lastfm