Fix mark addresses and add specs for addresses

Enables properly parsing marks as addresses. Also adds some specs for
addresses by checking how ex-mode behaves when used as a motion.

Fixes #70.

lib/command.coffee

@@ -24,7 +24,7 @@ class Command
       mark = @vimState.marks[str[1]]
       unless mark?
         throw new CommandError("Mark #{str} not set.")
-      addr = mark.bufferMarker.range.end.row
+      addr = mark.getEndBufferPosition().row
     else if str[0] is "/"
       addr = Find.findNextInBuffer(@editor.buffer, curPos, str[1...-1])
       unless addr?