try to reduce the number of allocations

[nbari]

When using named params (https://violetear.org/post/context-named/) the router uses 6 allocations, when not it uses 0.

$ make bench
go test -run=^$ -bench=.
2017/10/05 21:57:31 Adding path: /hello [GET,HEAD]
goos: darwin
goarch: amd64
pkg: github.com/nbari/violetear
BenchmarkRouterStatic-4         2017/10/05 21:57:31 Adding path: /hello [GET,HEAD]
2017/10/05 21:57:31 Adding path: /hello [GET,HEAD]
2017/10/05 21:57:31 Adding path: /hello [GET,HEAD]
2017/10/05 21:57:32 Adding path: /hello [GET,HEAD]
10000000               122 ns/op               0 B/op          0 allocs/op
2017/10/05 21:57:33 Adding path: /test/:word [GET,HEAD]
BenchmarkRouterDynamic-4        2017/10/05 21:57:33 Adding path: /test/:word [GET,HEAD]
2017/10/05 21:57:33 Adding path: /test/:word [GET,HEAD]
2017/10/05 21:57:33 Adding path: /test/:word [GET,HEAD]
2017/10/05 21:57:34 Adding path: /test/:word [GET,HEAD]
 2000000               913 ns/op             784 B/op          6 allocs/op
PASS
ok      github.com/nbari/violetear      4.144s

Try to optimize the router to do allocs as little as possible.

[nbari]

Currently using 0 allocs when using no context, using Name() automatically adds the route name to the context.

A slice could be used to reduce allocations instead of a map but the handlers will depend on GetParam and GetParams

tested but still the same like with the map, closing this for now