Improving track drawing

[kenlimmj]

When drawing the tracks I realize that most of the time I would just copy the stations, change data-pos to data-dest and setting the turning directions. In other words we can:

• Avoid namespacing data-dest and just reuse data-pos inside .subway-tracks
• Use the first <li> element for the starting point instead of declaring data-start-point so we don't spam the data-attribute list
• Based on the .redline .greenline classes from the other issue, have the option of automatically drawing track lines for each set. This way we don't need to explicitly draw the basic set of tracks (but this functionality can be kept for flexibility)

[kenlimmj]

On the note of the third point, realize it should be sort of like the subwaymap Java creator, where it would just... track its way through the list of stations predicting where it should turn. This might become processor intensive, so might be useful to offload the work to a webworker (detecting for support using Modernizr) where possible.