Go agent v1.0

Notes

• Removed BetaToken from the Config structure.
• Breaking Datastore change: datastore package contents moved to top level newrelic package. datastore.MySQL has become newrelic.DatastoreMySQL.
• Breaking Attributes change: attributes package contents moved to top level newrelic package. attributes.ResponseCode has become newrelic.AttributeResponseCode. Some attribute name constants have been shortened.
• Added "runtime.NumCPU" to the environment tab. Thanks sergeylanzman for the contribution.
• Prefixed the environment tab values "Compiler", "GOARCH", "GOOS", and "Version" with "runtime."