What are some alternatives?
Codeanywhere - Codeanywhere is a complete toolset for web development. Enabling you to edit, collaborate and run your projects from any device.
Plunker - Plunker is an online community for creating, collaborating on and sharing your web development ideas.
Coda - Text editor + file transfer + svn + CSS + Terminal + Books + More = Whoah. Welcome to Coda. Grow beautiful code.
CodePen - A front end web development playground.
AWS Cloud9 - AWS Cloud9 is a cloud-based integrated development environment (IDE) that lets you write, run, and debug your code with just a browser.