Changes

1. Remembers window position and size. NOTE: Doesn't still remember the sidebar width though. I'm working on that.
2. Add configuration option terminalRenderer: "canvas" | "webgl". 2.8.0 made WebGL as default renderer for terminal which seems to have caused some problems. Now the default renderer is back to canvas and folks who didn't have problem with terminals in 2.8.0 can use terminalRenderer: "webgl" in config.json file.