fix(common): remove obsolete marker trait

... and version-up right away :).

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 
 name = "yup-oauth2"
-version = "0.3.7"
+version = "0.3.8"
 authors = ["Sebastian Thiel <byronimo@gmail.com>"]
 repository = "https://github.com/Byron/yup-oauth2"
 description = "A partial oauth2 implementation, providing the 'device' authorization flow"

src/common.rs

@@ -1,11 +1,10 @@
 use chrono::{DateTime, UTC, TimeZone};
-use std::marker::MarkerTrait;
 use std::fmt;
 use std::str::FromStr;
 use hyper;
 
 /// A marker trait for all Flows
-pub trait Flow : MarkerTrait {
+pub trait Flow {
     fn type_id() -> FlowType;
 }