4.x - Remove pathFor() and rename relativePathFor() with relativeUrlFor()

[l0gicgate]

As per the discussion in #2493 and the stack overflow post explaining relative/absolute

relativePathFor() and pathFor() are getting entirely removed from the RouteParser component. Since this is a new interface that is the result of the fragmentation of the now deprecated Router component the user will need to re-learn the new interface so no point in implementing a warning of deprecation.

The RouteParser will now have this interface:

• RouteParser::fullUrlFor() - Absolute URL
• RouteParser::urlFor() - Root Relative URL formerly pathFor()
• RouteParser::relativeUrlFor() - Relative URL formerly relativePathFor()

[coveralls]

Coverage decreased (-0.002%) to 99.325% when pulling eb6a182 on l0gicgate:4.x-RefactorRouteParser into 65dd548 on slimphp:4.x.