performance: gjson parsing for readXLMeta, listParts, getObjectInfo. (#2631)

- Using gjson for constructing xlMetaV1{} in realXLMeta.
- Test for parsing constructing xlMetaV1{} using gjson.
- Changes made since benchmarks showed 30-40% improvement in speed.
- Follow up comments in issue https://github.com/minio/minio/issues/2208
  for more details.
- gjson parsing of parts from xl.json for listParts.
- gjson parsing of statInfo from xl.json for getObjectInfo.
- Vendorizing gjson dependency.

vendor/github.com/tidwall/match/README.md

@@ -0,0 +1,31 @@
+Match
+=====
+<a href="https://travis-ci.org/tidwall/match"><img src="https://img.shields.io/travis/tidwall/match.svg?style=flat-square" alt="Build Status"></a>
+<a href="https://godoc.org/github.com/tidwall/match"><img src="https://img.shields.io/badge/api-reference-blue.svg?style=flat-square" alt="GoDoc"></a>
+
+Match is a very simple pattern matcher where '*' matches on any 
+number characters and '?' matches on any one character.
+Installing
+----------
+
+```
+go get -u github.com/tidwall/match
+```
+
+Example
+-------
+
+```go
+match.Match("hello", "*llo") 
+match.Match("jello", "?ello") 
+match.Match("hello", "h*o") 
+```
+
+
+Contact
+-------
+Josh Baker [@tidwall](http://twitter.com/tidwall)
+
+License
+-------
+Redcon source code is available under the MIT [License](/LICENSE).