Make consolewriter colors default to true

src/consolewriter.ts

@@ -11,7 +11,7 @@ import {
 const browser = typeof window !== "undefined";
 
 export class ConsoleAdapter implements Adapter {
-   constructor(private colors?: boolean) {}
+   constructor(private colors: boolean = true) {}
 
    init(observable: ObservableInterface<Message>) {
       observable.subscribe(this.onMessage.bind(this));