[README] Add 'Build Status' badge.
[README] Add 'Build Status' badge.

benjaminhorner/RSDayFlow,ruslanskorb/RSDayFlow,aryaxt/RSDayFlow,akshitaagarwal1/RSDayFlow,benjaminhorner/RSDayFlow,emiliopavia/RSDayFlow,whatsahoy/RSDayFlow,lammertw/RSDayFlow,ruslanskorb/RSDayFlow,ruslanskorb/RSDayFlow-Mirror,RyanTech/RSDayFlow