Require go1.7 for compilation #2154

* Update the travis tests to exclude go1.6
  * Update the compile check to require go1.7+
  * Update misc go1.6 workarounds marked in the source

fs/fshttp/http.go

@@ -250,7 +250,7 @@ func cleanAuths(buf []byte) []byte {
 func (t *Transport) RoundTrip(req *http.Request) (resp *http.Response, err error) {
 	// Get transactions per second token first if limiting
 	if tpsBucket != nil {
-		tbErr := tpsBucket.Wait(context.Background()) // FIXME switch to req.Context() when we drop go1.6 support
+		tbErr := tpsBucket.Wait(req.Context())
 		if tbErr != nil {
 			fs.Errorf(nil, "HTTP token bucket error: %v", err)
 		}

fs/parseduration_test.go

@@ -49,7 +49,7 @@ func TestDurationString(t *testing.T) {
 		in   time.Duration
 		want string
 	}{
-		// {time.Duration(0), "0s"}, doesn't work on go1.6
+		{time.Duration(0), "0s"},
 		{time.Second, "1s"},
 		{time.Minute, "1m0s"},
 		{time.Duration(DurationOff), "off"},

fs/versioncheck.go

@@ -1,7 +1,7 @@
-//+build !go1.6
+//+build !go1.7
 
 package fs
 
-// Upgrade to Go version 1.6 to compile rclone - latest stable go
+// Upgrade to Go version 1.7 to compile rclone - latest stable go
 // compiler recommended.
-func init() { Go_version_1_6_required_for_compilation() }
+func init() { Go_version_1_7_required_for_compilation() }