Adds fields for RegD/US trading

• Adds isFund, commonName, infoUrl, usTradable, and accreditedOnly fields to assets
• Handles exceptions better

Miscellaneous Improvements

Merge pull request #3 from cfxmarkets/v1.4.x

Releasing v1.4.0

Upgrade to PHP7.1

v1.3.0

Updated to stable deps

Orders Datasource

This release focuses on implementing the Orders Datasource, allowing Brokerages to get, create and update orders on the Exchange.