Add close box option and ability to override close box label.
Fix Chrome bug: after clicking Next, reset hover state
when the trip block moves by re-creating the trip block.
Use CSS arrows instead of images.

This has 2 advantages:
- No delay when loading the arrow the first time.
- More flexibility for custom colors.
Merge pull request #13 from outright/enhancements

Enhancements and bug fixes, remove arrow images and add closeBoxLabel