docs(API): There must be an Oxford comma after "globalAPIs"

Verified necessity of Oxford comma after "globalAPIs" to clarify that "global APIs and testing mocks" are two separate objects.  (Source: https://owl.english.purdue.edu/owl/resource/607/01/)

Location of insertion:
![angular](https://cloud.githubusercontent.com/assets/5858247/3073888/f9e45100-e311-11e3-9f5c-748707bd147d.jpeg)