Get Rid of `fetch-ponyfill`

[bertybot]

The fetch-ponyfill causes me so many problems when developing with this package since it basically forces you to install node-fetch even if you don't need it. Making this package impossible to use in any JS environment besides node. Which is crazy because this package isn't even supposed to be used on node.

The fetch-ponyfill causes so much frustration and it's not even needed. Modern browsers and the LTS version of node include native-fetch. People who need the polyfill can pass it in the params, instead of forcing us all to install node-fetch