(rebased) ENH: Added more options for formats.style.bar
Author: Julien Marrec <julien.marrec@gmail.com>

Closes #14757 from jmarrec/style-bar and squashes the following commits:

dc3cbe8 [Julien Marrec] Added a whatsnew note
af6c9bd [Julien Marrec] Added a simple example before the parametric one
80a3ce0 [Julien Marrec] Check for bad align value and raise. Wrote test for it too
5875eb9 [Julien Marrec] Change docstrings for color and align
5a22ee1 [Julien Marrec] Merge commit '673fb8f828952a4907e5659c1fcf83b771db7280' into style-bar
0e74b4d [Julien Marrec] Fix versionadded
1b7ffa2 [Julien Marrec] Added documentation on the new df.style.bar options for align and Colors in the documentation.
46bee6d [Julien Marrec] Change the tests to match new float formats.
01c200c [Julien Marrec] Format flots to avoid issue with py2.7 / py3.5 compta.
7ac2443 [Julien Marrec] Changes according to @sinhrks: Raise ValueError instead of warnings when color isn’t a str or 2-tuple/list. Passing “base” from bar().
e3f714c [Julien Marrec] Added a check on color argument that will issue a warning. Not sure if need to raise TypeError or issue a UserWarning if a list with more than two elements is passed.
f12faab [Julien Marrec] Fixed line too long `git diff upstream/master | flake8 --diff now passes`
7c89137 [Julien Marrec] ENH: Added more options for formats.style.bar
673fb8f [Julien Marrec] Fix versionadded
506f3d2 [Julien Marrec] Added documentation on the new df.style.bar options for align and Colors in the documentation.
e0563d5 [Julien Marrec] Change the tests to match new float formats.
d210938 [Julien Marrec] Format flots to avoid issue with py2.7 / py3.5 compta.
b22f639 [Julien Marrec] Changes according to @sinhrks: Raise ValueError instead of warnings when color isn’t a str or 2-tuple/list. Passing “base” from bar().
3046626 [Julien Marrec] Added a check on color argument that will issue a warning. Not sure if need to raise TypeError or issue a UserWarning if a list with more than two elements is passed.
524a9ab [Julien Marrec] Fixed line too long `git diff upstream/master | flake8 --diff now passes`
d1eafbb [Julien Marrec] ENH: Added more options for formats.style.bar

 - [ ] closes #xxxx
 - [ ] tests added / passed
 - [ ] passes ``git diff upstream/master --name-only -- '*.py' | flake8 --diff``
 - [ ] whatsnew entry

cc @jmarrec here's a rebased version.

but if you have more changes you can push to your original branch.
