Update FAQ section

[indirect]

Add an FAQ to the bundler.io site with easily-linkable sections for quicker responses to common issues/questions.

See also the Trello card with the list of FAQs.

[richbowen]

What of the current FAQs, should they be replaced with these newer ones?

[TimMoore]

I don't think I realised there already is an FAQ!

Let's merge them... I think there's some overlap. We should also make sure that each question has an anchor so we can link to specific ones.

[coilysiren]

Trello card may disappear soon, so here's its content:

• Why aren't git gems (in my gem directory|visible in gem list|in my rbenv shims directory)?
• Shouldn't the github source use https instead of the git protocol?
• Versioning policy/breaking changes
• How should I get help?
• Why can't I override an incorrect dependency from a third-party gem?
• Should I commit my Gemfile.lock (can link to Yehuda's post)
• Why can't I use different versions of a gem in different platforms/groups?
• Why did running bundle update change a gem to an older version?
• Why don't I get the latest version of a gem when I run bundle install for the first time?
• Why can't I run bundle with sudo?

[arbonap]

👋🏽 So there's this trouble shooting guide in bundler repo's docs as well as this FAQ on bundler.io.
Do we want to combine the trouble shooting guide with the current FAQ, in addition to answering the questions from that Trello card (that haven't already been addressed) ?

I'd be happy to work on this issue.

[ianfixes]

Is this the FAQ in question? https://bundler.io/v2.0/guides/faq.html

Should I commit my Gemfile.lock (can link to Yehuda's post)

I submitted #487 for this