Integrate 'pre-commit'

This nifty tool provides a extensible way to configure pre-commit hooks
to do everything from running linters to spellchecking [1] and has
already been adopted by a few OpenStack projects [2]. Let's start using
it as a faster, more automatic alternative to the 'fast8' tox target and
iterate on it as we find more things to use it for. The 'fast8' target
is not deprecated though a note is included for end-users to alert them
to this great new tool.

Note that the 'check-executables-have-shebangs' actually failed and
highlighted that the 'contributor/development-environment.rst' document
was marked as executable when it shouldn't have been. This is corrected.

[1] https://pre-commit.com/
[2] https://review.opendev.org/#/q/file:.pre-commit-config.yaml

Change-Id: I256e75eceeb3495dce04885ca42d16adb4160cf3
Signed-off-by: Stephen Finucane <sfinucan@redhat.com>

.pre-commit-config.yaml

@@ -0,0 +1,21 @@
+---
+repos:
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v2.4.0
+    hooks:
+      - id: trailing-whitespace
+      - id: mixed-line-ending
+        args: ['--fix', 'lf']
+      - id: check-byte-order-marker
+      - id: check-executables-have-shebangs
+      - id: check-merge-conflict
+      - id: debug-statements
+      - id: flake8
+        additional_dependencies:
+          - hacking>=1.1.0,<1.2.0
+      - id: check-yaml
+        files: .*\.(yaml|yml)$
+  - repo: https://github.com/Lucas-C/pre-commit-hooks
+    rev: v1.1.7
+    hooks:
+      - id: remove-tabs