Refactor imports, Add vendor/ as submodule (#5)

refact imports to github.xxx. update go.mod + go.sum

* removed vendor/ folder

* Added vendor/ submodule.

Moved dependencies that need to be vendored into separate repository.
	- https://github.com/spdfg/elektron-vendor
Added vendor/ as a submodule using the below command.
	- git submodule add https://github.com/spdfg/elektron-vendor vendor
If wanting to use vendor, run the following commands after cloning
elektron.
1. git submodule init
2. git submodule update

* added instructions to clone vendor/ submodule.

* updated module to spdfg. Refactored imports

def/metric.go

@@ -1,4 +1,4 @@
-// Copyright (C) 2018 spdf
+// Copyright (C) 2018 spdfg
 // 
 // This file is part of Elektron.
 // 

def/sortingCriteria.go

@@ -1,4 +1,4 @@
-// Copyright (C) 2018 spdf
+// Copyright (C) 2018 spdfg
 // 
 // This file is part of Elektron.
 // 

def/sortingCriteria_test.go

@@ -1,4 +1,4 @@
-// Copyright (C) 2018 spdf
+// Copyright (C) 2018 spdfg
 //
 // This file is part of Elektron.
 //

def/task.go

@@ -1,4 +1,4 @@
-// Copyright (C) 2018 spdf
+// Copyright (C) 2018 spdfg
 // 
 // This file is part of Elektron.
 // 
@@ -24,8 +24,8 @@ import (
 
 	mesos "github.com/mesos/mesos-go/api/v0/mesosproto"
 	"github.com/pkg/errors"
-	"gitlab.com/spdf/elektron/constants"
-	"gitlab.com/spdf/elektron/utilities/offerUtils"
+	"github.com/spdfg/elektron/constants"
+	"github.com/spdfg/elektron/utilities/offerUtils"
 )
 
 type Task struct {

def/taskUtils.go

@@ -1,4 +1,4 @@
-// Copyright (C) 2018 spdf
+// Copyright (C) 2018 spdfg
 // 
 // This file is part of Elektron.
 // 

def/taskUtils_test.go

@@ -1,4 +1,4 @@
-// Copyright (C) 2018 spdf
+// Copyright (C) 2018 spdfg
 //
 // This file is part of Elektron.
 //

def/task_test.go

@@ -1,4 +1,4 @@
-// Copyright (C) 2018 spdf
+// Copyright (C) 2018 spdfg
 //
 // This file is part of Elektron.
 //
@@ -21,8 +21,8 @@ package def
 import (
 	"fmt"
 	mesos "github.com/mesos/mesos-go/api/v0/mesosproto"
+	"github.com/spdfg/elektron/constants"
 	"github.com/stretchr/testify/assert"
-	"gitlab.com/spdf/elektron/constants"
 	"reflect"
 	"testing"
 )