Replace Kadira Analytics with Galaxy APM

[remarcable]

In the past months, kadira was shut down. The guide doesn't reflect that yet.

It should be updated to show alternatives or to call attention to Galaxy's live monitoring.

[lorensr]

Thanks @lightningboss 😊

Maybe @rohit2b would be a good person to replace the Kadira section with a Galaxy APM section?

[rohit2b]

Thanks! I'll take this.

[greggman]

#665

[abernix]

Fixed by #665. Thanks, @greggman!