Fix minor error in +when: docstring (s/resolved/fulfilled/ in short description).
Fix minor error in +when: docstring (s/resolved/fulfilled/ in short description).

allen-zeng/PromiseKit,pgherveou/PromiseKit,allen-zeng/PromiseKit,pgherveou/PromiseKit,mxcl/PromiseKit,pgherveou/PromiseKit,mxcl/PromiseKit,mxcl/PromiseKit