Change command name in README.md
Change command name in README.md

The command got renamed in 5f017061.

cibernox/ember-cli-yuidoc,VladimirTyrin/ember-cli-yuidoc,cibernox/ember-cli-yuidoc,mixonic/ember-cli-yuidoc,greyhwndz/ember-cli-yuidoc,greyhwndz/ember-cli-yuidoc,mixonic/ember-cli-yuidoc,VladimirTyrin/ember-cli-yuidoc