hawaii state routes should not be US interstates

[nvkelso]

Basic Java string manipulation change.

Fixes #86

[bdon]

@nvkelso can you link some OSM examples so I can flesh out the test suite?

[nvkelso]

@bdon from the linked issue:

• https://www.openstreetmap.org/way/44750946#map=14/20.8742/-156.4637

With the following tags:

tag	value
highway	tertiary
lanes	2
name	South Wakea Avenue
ref	HI-3920

Where the ref should export as HI3920 (not HI-3920) and the network should be other (not US:I).

NOTE: A later change I'll propose will strip HI off the ref, and later more set the network to US:HI). So the test will be 3x useful :)

[bdon]

@nvkelso PTAL #114 - can encapsulate logic and test cases for HI-3920 -> HI3920