Updated prompt.py to match pep257 guidelines as described in #742.

When running tests on travis with python 3.6, I got the following
deprecationwarning in cookiecutter/repository.py:19:

    DeprecationWarning: Flags not at the start of the expression '\n(?x)\n((((git|hg)\\+)' (truncated)
    """)

Python 3.6 prefers the flags right at the start, so it doesn't allow a newline
in front of it.
I fixed it by adding the flag at the end, which is more clear/verbose in any
case. Which is fitting as the flag is `re.VERBOSE` :-)

Fix links to new core committers

added cookiecutter-django-dokku to README.rst

…y fix. (#1181)

Fixes: #1182

…ookiecutter templates.

The one in https://jinja.readthedocs.io/en/2.10/ does not exist.

as requested by @hackebrot

Some systems may have older virtualenv versions which would install
an ancient version of pip (like 8.1.1) which is not able to parse
requirements correctly generating errors like:

RequirementParseError: Expected ',' or end-of-list in pathlib2>=2.2.0;python_version<"3.6" at ;python_version<"3.6"
You are using pip version 8.1.1, however version 19.1.1 is available.

We cannot really support such versions so we can assure that we
only run with relatively newer tools.

This should fixed observed AppVeyor errors.

Require pip 9.0.0 or newer and upgrade virtualenv for tox envs

use context to close file nicely

…dule

Update file mode for hooks.py to be not executable

When we only have python3 installed, the test for missing argument is
failing because there is no "python" executable. Use `sys.executable`
instead. Also set environment correctly, like done in 7024d3b.

Use sys.executable when invoking python interpreter from tests

My contribution to Open Source.

Update README.md