Switch to gometalinter

Only small amount of required checks is enabled,
plan is to enable more linters as issues are fixed in the code.

http/fake.go

@@ -2,11 +2,12 @@ package http
 
 import (
 	"fmt"
-	"github.com/smira/aptly/aptly"
-	"github.com/smira/aptly/utils"
 	"io"
 	"os"
 	"path/filepath"
+
+	"github.com/smira/aptly/aptly"
+	"github.com/smira/aptly/utils"
 )
 
 type expectedRequest struct {