Recursive only if githubDiff, no anim if > 50

Only include github.js if in githubDiff mode
Only do recursive dir loading if in gitHub diff mode
Move folderItems splitting out of loop to avoid unnecessary processing
showFiles now begins the process of displaying files - animated into
view (using setInterval) if less than 50 items, or shows immediately (by
setting showContent and skipping recursion) if more
showNextFile() is a function to actually display a file or if the end,
kick off the process of adding deleted files/dirs