Revert of Check in a simple pure-python based Markdown previewer.

tools/md_browser/README.md

-# md_browser
-
-This is a simple tool to render the markdown docs in a chromium checkout
-locally. It is written in Python and uses the Python 'markdown' package,
-which is checked into src/third_party.
-
-md_browser attempts to emulate the flavor of Markdown implemented by
-[Gitiles](https://gerrit.googlesource.com/gitiles/+/master/Documentation/markdown.md).
-
-Gitiles is the source browser running on https://chromium.googlesource.com,
-and can be run locally, but to do so requires a Java install and a Buck
-install, which can be slightly annoying to set up on Mac or Windows.
-
-This is a lighterweight solution, which also allows you to preview uncommitted
-changes (i.e., it just serves files out of the filesystem, and is not a
-full Git repo browser like Gitiles is).
-
-To run md_browser:
-
-1. cd to the top of your chromium checkout
-
-2. run `python tools/md_browser/md_browser.py`
-
-3. There is no step three.
-
-This will run a local web server on port 8080 that points to the top
-of the repo.  You can specify a different port with the `-p` flag.