Moving holding hands illustration to 'start a cluster' page. It didn't quite fit the 30 second tutorial (and had style problems because of code block overlap).
Merge pull request #333 from rethinkdb/slava_moving_illustration

Moving holding hands illustration to 'start a cluster' page.
fixing typo 'exmple'
Merge pull request #341 from rethinkdb/grey_example_typo_fix

Fixing 'exmple' typo
Updating migration doc as mentioned in #231
Updating migration doc with Michels comments
Merge branch 'master' into v1.13
Merge branch 'slava_migration' into v1.13