Revert of Check in a simple pure-python based Markdown previewer. (patchset #3 id:90001 of https://codereview.chromium.org/1356203004/ )

Reason for revert:
checklicenses.py is complaining:

http://build.chromium.org/p/chromium/builders/Linux/builds/67561

Original issue's description:
> Check in a simple pure-python based Markdown previewer.
>
> We are now trying to write more and more of our documentation
> as Markdown files that live in the repo, but there's no easy
> way to preview changes in a local checkout.
>
> This CL adds a simple previewing tool written in pure Python
> that depends on the 'Markdown' python package (also pure Python)
> to do all the heavy lifting. It aims to replicate the look
> and feel of googlesource.com as closely as possible.
>
> R=nodir@chromium.org, jam@chromium.org
> BUG=
>
> Committed: https://crrev.com/abe11cb68dd11d5ee153218ba99a3cdba3a3ced6
> Cr-Commit-Position: refs/heads/master@{#352450}

TBR=nodir@chromium.org,jam@chromium.org,scottmg@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=

Review URL: https://codereview.chromium.org/1389543003

Cr-Original-Commit-Position: refs/heads/master@{#352503}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: f87211d56e86be9d68e637e47e7fdfbbcb8834d6