Move the window: the header is the title bar

As of 1.4.0, the BookProofs header doubles as the window's title bar, which gives the canvas a little more room. Drag the project or book name, the logo, or any empty part of the header to move the window, and double-click it to zoom, just like a normal title bar. On Mac the window buttons sit at the left of the header; on Windows the minimize, maximize and close buttons sit at its right.