doc: tweak API doc
doc: tweak API doc

- clean up style of headers, response codes, request formats
- move reference info (pagination, errors, etc) to end of doc

jonboulle/fleet,improbable-io/fleet,webwlsong/fleet,endocode/fleet,mwitkow-io/fleet,hhoover/fleet,endocode/fleet,coreos/fleet,dongsupark/fleet,coreos/fleet,giantswarm/fleet,mwhooker/fleet,dalbani/fleet,mwitkow/fleet,esatterwhite/fleet,octoblu/fleet,coreos/fleet,improbable-io/fleet,wuqixuan/fleet,flandr/fleet,mookjp/fleet,wuqixuan/fleet,mookjp/fleet,paveltiunov/fleet,webwlsong/fleet,ecnahc515/fleet,esatterwhite/fleet,bviswana101/fleet,paveltiunov/fleet,improbable-io/fleet,mwitkow/fleet,mischief/fleet,jonboulle/fleet,ecnahc515/fleet,octoblu/fleet,giantswarm/fleet,thepwagner/fleet,jonboulle/fleet,endocode/fleet,hhoover/fleet,bviswana101/fleet,ecnahc515/fleet,WPMedia/fleet,thepwagner/fleet,dongsupark/fleet,dalbani/fleet,WPMedia/fleet,mwhooker/fleet,bcwaldon/fleet,flandr/fleet,mwitkow-io/fleet,mischief/fleet,giantswarm/fleet,dalbani/fleet,bcwaldon/fleet,dongsupark/fleet,bcwaldon/fleet