Renames: lib/src/data-structure.dart -> lib/src/data_structure.dart
Fixes a null object bug in lane.dart
SourceJoint has a dispatch limit and will stop glowing when limit is reached
Vehicle has velMax and accMax
Driver sees the front car and can look over the next lane
Fixes a bug in driver that it only chooses a random lane once
Fixes a bug in SourceJoint that total transparent glow may blink suddenly
Add Color class to represent and manage color
Randomize the label circle color of SourceJoint
Fixes the problem of displaying small font in Chrome.

Use larger font first then scale down to workaround the minimum font
size problem in Chrome (or maybe all webkit browsers).

Thanks to Joachim Sauer:
http://stackoverflow.com/questions/6304720/is-there-a-way-to-override-the-minumum-font-size-in-webkit-browsers