Added note about breaking changes in v0.13.0
Added note about breaking changes in v0.13.0

Additionally, I moved the breaking changes to the top of the list so that they
were more obvious.

akshatnitd/axios,mzabriskie/axios,renzhaozhao/axios,akshatnitd/axios,mzabriskie/axios,nickuraltsev/axios,axios/axios,mzabriskie/axios,nickuraltsev/axios,nickuraltsev/axios,axios/axios,akshatnitd/axios,renzhaozhao/axios,axios/axios,renzhaozhao/axios