Release 7.7.0

Fixes:

  + The `selinux` configuration steps may sometimes fail. Our customers always end up disabling `selinux`, so let's do it in the installer (the same goes for apparmor).
  + The changelog was obsolete (not up to date); remove it.
  + Submit a bit more data in automated error reporting (OS details).
  + Add checks in the install script for both root and supported OS (we received automated error reports for installs attempted on Amazon Linux).
  + Log unexpected errors in the `scalr-manage` script (it has substantial test coverage, but logging those errors really isn't difficult, so it's worth it).
  + Add a `match-version` command to `scalr-manage` that checks whether a suitable configuration already exists on the system (so, if an installation fails, users can run `dist/install.sh` again and we preserve their configuration, but if we push an update, they are prompted to re-create their configuration). This helps if we receive an automated error report that has to do with attributes (like we had with IPv6 detection). This can be extended in the future to only prompt users if we did something that had to do with `configure`. 
  + Fix a cleanup issue in tests.