Re-enable metadata

This is a simplistic Hash parser, but it works for basic metadata
purposes which seems better than having no metadata support at all.  The
following examples show how to set a page title using metadata.

All on one line:

<!-- --- title: My Fantastic Page -->

Or split across multiple lines:

<!-- ---
title: My Fantastic Page
-->

Notes:

1. Only one key/value pair per line. Multiple lines must be used for
multiple key/value pairs (though I'm not aware of support for any keys
other than "title").

2. Keys and values cannot contain embedded newlines.

3. The patch does *not* HTML-sanitize the key or value portion of the
metadata.  Presumably metadata is not solely for inclusion in HTML, so
only the user of the metadata will know whether it needs to be sanitized
in any way.
Strip text resembling HTML tags from metadata

Each line of a metadata block has all HTML-like tags removed before
parsing.  Basically this removes all text contained between and
including '<' and '>', but it is not "greedy".  For example, the
metadata:

title : The <, ==, >, and <=> Operators

would be stripped to:

title : The , and  Operators

It would NOT be stripped to:

title : The  Operators

The metadata test have also been re-enabled.
Merge upstream changes
Fix wording of metadata stripping test caption
Merge pull request #30 from david-macmahon/master

Re-enable metadata (try 2)