Add IPv6 column in list and remove dead instance

This is done after some complaints I saw on Twitter about the lack of IPv6 support on Mastodon instances.
Also, seeing this may encourage instances owner to add IPv6 support to their own.

Updated out-of-date info for gay.crime.team

improve video button visibililty (issue #713)

Add social.targaryen.house to instances list

Add mastodon.xyz to instances list

Put line breaks between API methods in docs

Clarify post privacy warning

Mastodon is not an alternative, it is a solution

This month I traveled to Cambridge, Massachusetts with my friends and attended LibrePlanet 2017. At the talk *Technology for direct actions*, Andrew Seeder pointed out that we often call free software an "alternative" to what exists. But an alternative is something that is mostly similar, and differentiated by preference rather than need. For instance, a trackball is an alternative to a mouse, but a jail is not an alternative to a bedroom. Andrew suggested that we start looking at free software as "solutions" rather than alternatives. So I propose boldly proclaiming that Mastodon is not an alternative to Twitter, but rather a solution to it.

Needs to be a separate task with no locking

Update amaroq name

I was informed that the current warning if you @ a remote server in a private post is inadequate. These are suggested changes to better inform users.