Support Helmet v5, add include/exclude support, fix express 200.html rendering, only crawl potential html pages

[CodyRay]

Apologies, it seems I have put a lot into this PR. I was kind of on a roll though. I tried to test as many configurations as I could and it seems pretty stable.

Note: I went ahead and renamed the path option to include since it wasnt documented and it appears react-snapshot hasnt been released yet. But I can make that backward compatible as well...

Fixes #17
Fixes #19
Incorporated #23 and #22
Fixes #15 and #16 in a few more cases, also handles includes and excludes for basenames
Closes #11

Also various other things I found

• Only crawl potential html pages (not links to .jpg files for instance)
• Release resources so that the server can gracefully shutdown
• Removed hardcoded port
• Updated readme

[geelen]

Hey! Thanks for this! I'd actually done a little bit of work myself on a few of those, but hadn't finished and merged it. I've just done so now at #26

There were a few merge conflicts but I've fixed them and pushed the code on the haroldhues-master branch (also pointed #27 at it). I'm seeing an error with ext.pathname in my local testing, can you take a look and see if maybe something got broken in the merge?

Very keen to get a new release out with these changes in the next few days. Thanks again for picking up a bunch of things at once 👌

[CodyRay]

@geelen Path problem is fixed, I could not get connect-history-api-fallback to work with my project. I didn't look into it too much, but I replaced it with a simple middleware that I believe will do the same thing. I didn't test if the proxy still works. 🙈

BTW create-react-app also supports passing an object to proxy. It might be worth handling that case as well

[geelen]

Closing in favour of #27

[geelen]

Boom. Finally figured out the bugs with this, and have merged & published v1.1.0