fix: regression in vars extract for wildcard host (gorilla#579)

Continuing from PR gorilla#447 we have to add extra
check to ignore the port as well

add tests to cover this case

perf: reduce allocations in (*routeRegexp).getURLQuery (gorilla#544)

A production server is seeing a significant amount of allocations in (*routeRegexp).getURLQuery

Since it is only interested in a single value and only the first value we create a specialized function for that.

Comparing a few parameter parsing scenarios:

```
Benchmark_findQueryKey/0-8 	 7184014	       168 ns/op	       0 B/op	       0 allocs/op
Benchmark_findQueryKey/1-8 	 5307873	       227 ns/op	      48 B/op	       3 allocs/op
Benchmark_findQueryKey/2-8 	 1560836	       770 ns/op	     483 B/op	      10 allocs/op
Benchmark_findQueryKey/3-8 	 1296200	       931 ns/op	     559 B/op	      11 allocs/op
Benchmark_findQueryKey/4-8 	  666502	      1769 ns/op	       3 B/op	       1 allocs/op

Benchmark_findQueryKeyGoLib/0-8 	 1740973	       690 ns/op	     864 B/op	       8 allocs/op
Benchmark_findQueryKeyGoLib/1-8 	 3029618	       393 ns/op	     432 B/op	       4 allocs/op
Benchmark_findQueryKeyGoLib/2-8 	  461427	      2511 ns/op	    1542 B/op	      24 allocs/op
Benchmark_findQueryKeyGoLib/3-8 	  324252	      3804 ns/op	    1984 B/op	      28 allocs/op
Benchmark_findQueryKeyGoLib/4-8 	   69348	     14928 ns/op	   12716 B/op	     130 allocs/op
```

Update stale.yml (gorilla#494)

host:port matching does not require a :port to be specified.

In lieu of checking the template pattern on every Match request, a bool is added to the routeRegexp, and set
if the routeRegexp is a host AND there is no ":" in the template. I dislike extending the type, but I'd dislike
doing a string match on every single Match, even more.

[build] Remove sudo setting from travis.yml (gorilla#462)

replace rr.HeaderMap by rr.Header() (gorilla#443)

[docs] Improve docstrings for middleware, skipclean (gorilla#375)

[feat] Add middleware support as discussed in gorilla#293 (gorilla#294)

* mux.Router now has a `Use` method that allows you to add middleware to request processing.

MatchErr is set to ErrNotFound if NotFoundHandler is used (gorilla#311)

[docs] README.md: add missing `.` (gorilla#292)