minor change to beautifier - ignore colons inside strings

The new colon-based alignment was also aligning colons in strings, as follows:

   (&img style:(+ "height:60px; width:60px; "
                   "float:right; background-color:#FFF; "
                 "padding:0.5px; margin:5px; "
           "border-radius: 16.67%; "
              "box-shadow: 0px 0px 1px #AAA;")
           src:(app artworkUrl60:))

This didn't seem good to me, so now colons inside strings are ignored for the purposes of alignment.

   (&img style:(+ "height:60px; width:60px; "
                  "float:right; background-color:#FFF; "
                  "padding:0.5px; margin:5px; "
                  "border-radius: 16.67%; "
                  "box-shadow: 0px 0px 1px #AAA;")
           src:(app artworkUrl60:))