More verbose error messages from transactionBuilder.send

Possible breaking change if you were relying on "TypeError: Failed to fetch" anywhere in your code to detect errors.

Creating a release because this could have breaking changes.

The Masternode_API send method now checks the response code === 200 and then returns the json information. For all other status codes it attempts to get the statusText and return that as an error.
The transactionBuilder send method had an bug checking if the response as undefined. That has been fixed and now, if the response is undefined, it will return "TypeError: Failed to fetch" like it did before. There is now a change where if response is a string (so NOT the JSON response) it will return that as the error. This string error would be the statusText passed in from the Masternode_API.