Multiple fixes/changes

[mbainrot]

• Fixed various issues with building and CI due to the amount of things that have changed around this since the last change.
• Fixed issue that is currently breaking MHVDB2 (SSL verification failure due to python for some reason being unable to use the OS certs to verify mailgun's SSL cert). Fixed this by at build time generating a /usr/lib/ssl/certs/bundle.CA_BUNDLE and setting verify='/usr/lib/ssl/certs/bundle.CA_BUNDLE' in the requests.post() function in mailer.py
• Finally addressed issue with my #104 PR which @brendam highlighted. No matter what the user puts in, it will always be treated as lower case. Existing data in the database will be corrected as users renew their memberships 😄
• Optimised a little bit of the Dockerfile, relates to #92
• Breaking change - FROM address for mailer is now derrived from settings.py, I did this so I could test without impersonating noreply@makehackvoid.com and w/o accidentially committing my test mailgun account email addr to git.
• Updated settings.py.sample to reflect the above

Appologies to everyone for all the email spam (if any) while I learneded to git again 😃

p/s ping @jamiereid

[jamiereid]

Hi Max. Thanks for the PR! I wanted to acknowledge it, and say that I havn't had time to review, but will make some time on the weekend unless someone beats me to it. -J

[mbainrot]

Thanks Jamie!

The main thing I need cross checked is it's ""live"" functionality as I did manage to break the build in one of my iterations leading up to my PR without Jenkins failing the build. I think this happened because either Jenkins doesn't test all of the possible points or because it doesn't test it live. I did some testing myself but I don't trust my tired eyes so I'd very much appreciate a peer review to make sure I am not a muppet 😄

p/s when I say live I mean like with the consortium of services running together, not production, I may be crazy but I ain't that crazy 😛