Make shape fields explicitly nullable

This adds compatibility for HHVM >= 3.23 and removes compatibility
for HHVM < 3.23.

Make RouteCollector members protected

Have git ignore composer files

Not sure why there isn't one already. Just more convenient, I think.

Use type-strict comparison

Add example for multiple optional parts

Add fallback routes matching *any* method

These are strictly fallback handlers and only match after all other
routes have been tried. The target use case are path-specific 404
pages or similar.

Merge pull request nikic#83 from fredemmott/fastroute-hhi

HHI: Change the options arrays for dispatchers to shapes

Simplify implementation for optionals

Drop the manual parsing code, use regex.

Fix issue nikic#50

If the static route doesn't exist for the given method, try matching
against dynamic ones as well. Allowed methods are now collected from
both static and dynamic routes.

This changes the route data format, so cache is no longer valid --
maybe include a version identifier in the cache file?

Add PHP 7 to Travis