Using double quotes for xcodebuild args

This fixed a problem I had where one of my targets' names looked like this: `StMary's`

So essentially xcodebuild was looking like this: `xcodebuild ... -scheme 'StMary's'` causing it to error out.

I went ahead and used double quotes on all of the xcodebuild arguments to ensure any wild apostrophes wouldn't break. I only tested this on my personal project where this matters - so I'm not sure about total coverage right now.