CSS Fixes and Tweaks
- New progress style (which also fixes an alignment issue)
- Fix spacing of `<pre><code>` blocks
- Better looking admonition (that doesn't interfere with other element's styling)
Remove now obsolete admontionicon extension
- admonition icons are now added with pure css
Upgrade PyMdown extensions
- b64: run as a post processor to catch all possible paths
- githubemoji: upgrade to latest (no functional changes)
- headeranchor: Add itself without needing changes to toc extension
- magiclink: Even better regex rules
- tasklist: No functional changes
- progressbar: Now requires title to be quoted (no longer optional).  Inline settings support is removed in favor of using inline attr_list support (new).  Syntax now requires only one equal sign, but can take any number now.  addclasses and levelclass settings renamed to add_classes and level_class.

Related changes:
- toc reverted to its original form as it no longer conflicts with headeranchor
- Update test.md
Better plain html and base64
- Don't bother with comments in base64 conversion
- Remove comments when stripping for plain html
Add superfences (with uml support)

- Add superfineness which adds nested fenced blocks and flowchart and
sequence diagrams
- Add HTML to load um javascript and convert the uml content into
diagrams
- Include flowchart.js since there are no available cdn for it
Add `enable_pygments` option

- Allow the enabling and disabling of pigments usage
Remove b64 as it isn't needed
- b64 is implemented directly in Markdown Preview, so a separate extension for b64 is redundant
Path Conversion Updates
- Fix basepath regeression
- Better absolute path: ignore paths in comments, quote paths
- Add relative path: TODO: needs output relative param
Fix missed quote change
Update to latest github syntax styes

- Upgrade github.css to latest
https://github.com/sindresorhus/github-markdown-css
- Upgrade Pygments style for Python Markdown to Github’s last Pygments
style before abandoning Pygments.
- Move original github style to “githubclassic”.
Finish up relative path support
Remove debug
Update test file
Handle html fragments appended to paths

- When converting html links to absolute or relative, allow things like
header specifiers: “#some-header” or queries etc.  Convert only the
path, and leave the fragment intact.
Make sure abs path is valid
Add superfences to github extension
Update read

- Add included 3rd party extensions  in a table
- Reference an extensions documentation if they have their own.
- ProgressBar extension has its own document page, so don’t include
info in the main read.
- Remove references to obsolete extensions.
- Mention how to define multiple options for codehilite (some people
have found this confusing).
Small updates to test.md

- Superfences is already loaded in github
- Update some incorrect info and clarify some others
Merge pull request #253 from facelessuser/master

Bug Fixes and New Features