Update CanonURL.php

Fixing a security issue
Update README

Removed some extra lines.
Updated for 0.2
Update README.md

removed some blank lines
Bump version to 0.2

Follows-up 4eaaebca63.
(issue #1) Escape url before outputting in attribute.
(issue #2) Use Title::getCanonicalURL instead of $CanonBaseURL
Clean up, fix #3. Bump version to 0.2.0

* Indentation and whitespace
* Prefix global function with ef per MediaWiki convention
* Use OutputPage::setCanonicalUrl to avoid adding a second
  rel=canonical if MediaWiki core adds one already (fixes #3).
* Include patch version (".0") per semver guidelines.
* Prefer HTTPS urls for pages on servers that support it.
* Fix syntax in README.md to be proper Markdown, it currently
  looks broken when rendered on GitHub.
* Turn README.md into a symlink instead of duplicating the content.