Update documentation.md

I found that I needed this package locally or I got this error: `ImportError: Failed loading extension 'pymdownx.superfences' from 'pymdownx.superfences', 'markdown.extensions.pymdownx.superfences' or 'mdx_pymdownx.superfences'` when trying to build

hook_civicrm_apiWrappers: More tweaks

This commit mostly adds Markdown tweaks.

I also struck the comparison to pre/post hooks... because I enjoy removing words. 

hopefully improve the docs on API_Wrappers

typo in method-name

for non civicrm links class=no-popup is needed

related to https://issues.civicrm.org/jira/browse/CRM-20187

added angular

Styleguide To Do

extension lifecycle - add formal review process

content from:
https://docs.google.com/document/d/1nUfSqIpMQplrj6cv4Nvkxf-dR3NClghhKdB_Xw3MpYY/edit
No substantive content changes, but quite a bit of content clean up
during import

Fixing link for User Guide :: English :: latest

Added Limitations section

since these list items are all also headings and thus will appear in the
TOC nav on the right side of the page

Closes #90

clarify form/bao role

Fixes #79

per comments from @eileen here https://github.com/civicrm/api4/issues/14#issuecomment-278860730

mkdocs.yml - Rearrange top level of TOC

fixes #84