use t.Run for tests

using `t.Run` instead including the test name in error message is
a more idiomatic way of testing things in go. Since this feature
was added to go in 1.7 release and the travis config explicitly
specifies 1.4 and 1.5 (2 and 2,5 year old releases) as test targets
this change will break the CI builds, therefore this commit also
proposes dropping those releases in favour of adding a newer
version of go (1.8) as the test target.

Signed-off-by: Sevki <s@sevki.org>

.travis.yml

@@ -1,8 +1,7 @@
 language: go
 sudo: false
 go:
-  - 1.4
-  - 1.5
+  - 1.8
   - tip
 before_install:
   - go get github.com/axw/gocov/gocov

main_test.go

@@ -16,9 +16,7 @@ limitations under the License.
 
 package jsonnet
 
-import (
-	"testing"
-)
+import "testing"
 
 // Just a few simple sanity tests for now.  Eventually we'll share end-to-end tests with the C++
 // implementation but unsure if that should be done here or via some external framework.
@@ -52,18 +50,21 @@ var mainTests = []mainTest{
 
 func TestMain(t *testing.T) {
 	for _, test := range mainTests {
-		vm := MakeVM()
-		output, err := vm.EvaluateSnippet(test.name, test.input)
-		var errString string
-		if err != nil {
-			errString = err.Error()
-		}
-		if errString != test.errString {
-			t.Errorf("%s: error result does not match. got\n\t%+v\nexpected\n\t%+v",
-				test.input, errString, test.errString)
-		}
-		if err == nil && output != test.golden {
-			t.Errorf("%s: got\n\t%+v\nexpected\n\t%+v", test.name, output, test.golden)
-		}
+		t.Run(test.name, func(t *testing.T) {
+			vm := MakeVM()
+			output, err := vm.EvaluateSnippet(test.name, test.input)
+			var errString string
+			if err != nil {
+				errString = err.Error()
+			}
+
+			if errString != test.errString {
+				t.Errorf("%s: error result does not match. got\n\t%+v\nexpected\n\t%+v",
+					test.input, errString, test.errString)
+			}
+			if err == nil && output != test.golden {
+				t.Errorf("got\n\t%+v\nexpected\n\t%+v", output, test.golden)
+			}
+		})
 	}
 }