Convert all links to HTTPS

[cookieguru]

Thank you for contributing to A Field Guide to Elephpants. To speed up approval of your contribution, please review the following checklist:

• I have read the CONTRIBUTING guide
• All text and photographs included are licensed under CC:BY-NC-SA or a compatible license.
• (If Needed) New subspecies have been added to sculpin_site.yml following the naming convention.

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This PR converts all http:// links to https:// except for:

• source/index.html: http://www.elroubio.net/ (site has open port 443 but SSL handshake failed)
• source/_elephpants/2015-10-13-multicolored-haphpy.md: https://github.com/afup/haphpy-birthday is using GitHub Pages but is not configured to serve via the haphpy-birthday.net domain
• various links in composer.lock from 3rd party libraries

[cookieguru]

@Wilkins do you still have the original files? These links are dead

afieldguidetoelephpants/source/_elephpants/2014-09-05-red-laravel.md

Line 12 in 504d874

link: http://wilkins.fr/elephpants/IMG_4326.JPG

afieldguidetoelephpants/source/_elephpants/2014-09-05-red-laravel.md

Line 16 in 504d874

link: http://wilkins.fr/elephpants/IMG_4325.JPG

[Wilkins]

Hello @cookieguru 😄

I do have the files.
In fact the links are OK with www :
http://www.wilkins.fr/elephpants/IMG_4326.JPG
http://www.wilkins.fr/elephpants/IMG_4325.JPG

and the small versions :
http://www.wilkins.fr/elephpants/IMG_4326_SMALL.JPG
http://www.wilkins.fr/elephpants/IMG_4325_SMALL.JPG

But my local hosting is not handling HTTPS right now.
If you have a place to put them on an HTTPS hosting, you are welcome to copy them.

Ping me if you need anything else 😄