Removed some trailing whitespace causing a build break on OSX

*Before:*

Checking for JS errors...
src/MarkerClusterGroup.js	line 684	col 1	 Trailing whitespace.
src/MarkerCluster.js	line 132	col 1	 Trailing whitespace.
src/MarkerCluster.Spiderfier.js	line 246	col 1	 Trailing whitespace.
3 error(s) found.

jake aborted.

*After:*

Checking for JS errors...
	Check passed
Concatenating 5 files...
	Uncompressed size: 53134 bytes (+0)
	No changes
Compressing...
	Compressed size: 26102 bytes (+0)
	No changes