Remove tags in page.title between <title> and </title>

Page.title can have tags when the title starts with ALL CAPITAL WORD.
In my case, a markdown file has title info:

Title: MMIX Getting started

and generated html has title tag like this:

    <title><span class='caps'>MMIX</span> ... </title>

this makes browser tab ugly.
I don't know if there are other cases.
Anyway, I think it's good to strip tags in title tags.

p.s. my pelican version is 3.3.0