Import context from standard package (#101)

* Import context from standard package.

Author: avishalom

auth/auth.go

@@ -16,6 +16,7 @@
 package auth
 
 import (
+	"context"
 	"crypto/rsa"
 	"encoding/json"
 	"errors"

auth/auth_appengine.go

@@ -17,7 +17,7 @@
 package auth
 
 import (
-	"golang.org/x/net/context"
+	"context"
 
 	"google.golang.org/appengine"
 )

auth/auth_std.go

@@ -16,7 +16,7 @@
 
 package auth // import "firebase.google.com/go/auth"
 
-import "golang.org/x/net/context"
+import "context"
 
 func newSigner(ctx context.Context) (signer, error) {
 	return serviceAcctSigner{}, nil

auth/auth_test.go

@@ -15,6 +15,7 @@
 package auth
 
 import (
+	"context"
 	"encoding/json"
 	"errors"
 	"fmt"

auth/user_mgt.go

@@ -15,6 +15,7 @@
 package auth
 
 import (
+	"context"
 	"encoding/json"
 	"fmt"
 	"net/http"

auth/user_mgt_test.go

@@ -16,6 +16,7 @@ package auth
 
 import (
 	"bytes"
+	"context"
 	"encoding/json"
 	"fmt"
 	"io/ioutil"

firebase.go

@@ -18,6 +18,7 @@
 package firebase // import "firebase.google.com/go"
 
 import (
+	"context"
 	"encoding/json"
 	"errors"
 	"io/ioutil"

firebase_test.go

@@ -15,6 +15,7 @@
 package firebase
 
 import (
+	"context"
 	"fmt"
 	"io/ioutil"
 	"log"

iid/iid.go

@@ -16,6 +16,7 @@
 package iid // import "firebase.google.com/go/iid"
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"net/http"

iid/iid_test.go

@@ -15,6 +15,7 @@
 package iid
 
 import (
+	"context"
 	"fmt"
 	"net/http"
 	"net/http/httptest"