.moban.yaml: Use moban's new requires syntax to reference a git repo as dependency

Moban version 0.3.x support git repo as dependency, and moban configuration file can be located in git repo too. Hence the syntax here should be updated. The benefit is that moban v0.3.x will takes care of common git repos and share them with all coala project that reference the common repo(s), i.e. coala-mobans. The common repos are store in ~/.mobans/repos.