pkg/util/{ip.go,url.go}: Fix some golint issues

See,
$ gometalinter --vendor --deadline 10m --disable-all --enable=golint  ./...
ip.go:8:6⚠️ func SplitIpPort should be SplitIPPort (golint)
url.go:14:6⚠️ func NewUrlQueryReader should be NewURLQueryReader (golint)
url.go:9:6⚠️ type UrlQueryReader should be URLQueryReader (golint)
url.go:37:6⚠️ func JoinUrlFragments should be JoinURLFragments (golint)

pkg/api/render.go

@@ -14,7 +14,7 @@ import (
 )
 
 func (hs *HTTPServer) RenderToPng(c *m.ReqContext) {
-	queryReader, err := util.NewUrlQueryReader(c.Req.URL)
+	queryReader, err := util.NewURLQueryReader(c.Req.URL)
 	if err != nil {
 		c.Handle(400, "Render parameters error", err)
 		return