Add Register() with req/resp structs

requests.go

@@ -0,0 +1,11 @@
+package gomatrix
+
+// ReqRegister is the JSON request for http://matrix.org/docs/spec/client_server/r0.2.0.html#post-matrix-client-r0-register
+type ReqRegister struct {
+	Username                 string      `json:"username,omitempty"`
+	BindEmail                bool        `json:"bind_email,omitempty"`
+	Password                 string      `json:"password,omitempty"`
+	DeviceID                 string      `json:"device_id,omitempty"`
+	InitialDeviceDisplayName string      `json:"initial_device_display_name"`
+	Auth                     interface{} `json:"auth,omitempty"`
+}