Add Zap support for Fiber.

[efectn]

Faster than Fiber's offical logger.

Offical:

Running 20s test @ http://localhost:3000/
  2 threads and 128 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency     3.30ms    3.56ms  24.78ms   85.56%
    Req/Sec    23.18k     1.75k   27.35k    70.00%
  923992 requests in 20.05s, 114.55MB read
Requests/sec:  46078.06
Transfer/sec:      5.71MB

Fiberzap:

Running 20s test @ http://localhost:3000/
  2 threads and 128 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency     1.27ms    1.01ms  11.84ms   76.41%
    Req/Sec    41.93k     3.59k   50.16k    78.25%
  1671296 requests in 20.06s, 207.20MB read
Requests/sec:  83330.87
Transfer/sec:     10.33MB

But i need to decrease allocs/op, B/op and ns/op before the merging it. I need your reviews to fix it :)

{"level":"info","msg":"Success","latency":"103ns","status":200,"method":"GET","url":"/"}
{"level":"info","msg":"Success","latency":"101ns","status":200,"method":"GET","url":"/"}
{"level":"info","msg":"Success","latency":"94ns","status":200,"method":"GET","url":"/"}
  331002	      3731 ns/op	     261 B/op	       2 allocs/op
PASS

[Jictyvoo]

I put some comments.I don't know very much about this logger, sorry if I'm saying something wrong

[ReneWerner87]

@Jictyvoo can you check the stuff again -> when you approve it, i will merge it

[efectn]

@Jictyvoo can you check the stuff again -> when you approve it, i will merge it

I need to recheck benchmarks before merging it. Can you wait a bit?

[ReneWerner87]

sure

[efectn]

@ReneWerner87 @Jictyvoo I think everything is OK.