Change "Icon" to "Icon^M^M", add .VolumeIcon.icns .fseventsd

#### Icon^M^M
See http://blog.bitfluent.com/post/173740409/ignoring-icon-in-gitignore:
The actual file name is "Icon\r" with a CRLF(!). You have to enter two literal ^M control characters to match CRLF.
"Icon" would also ignore e.g. a "Icons" directory etc.

#### .VolumeIcon.icns
See http://superuser.com/a/298798:
Changing a volume's icon creates a hidden .VolumeIcon.icns file instead of Icon^M^M.

#### .fseventsd
fseventsd is the file services events daemon. (See http://en.wikipedia.org/wiki/FSEvents, https://developer.apple.com/library/mac/documentation/Darwin/Conceptual/FSEvents_ProgGuide/FileSystemEventSecurity/FileSystemEventSecurity.html)