By Karissa Bell
Twitter has had a complicated relationship with developers.
In its earlier days, the social network encouraged third-party developers to build their own apps and services on top of the platform. But the company later began to roll out its own competing features (the most notable example of this is when Twitter created its own image sharing service, frustrating companies like Twitpic and Yfrog).
But Twitter made its biggest appeal yet to developers on Wednesday at Flight, the company’s first mobile developer conference. There CEO Dick Costolo …