compiler: move it up from vm

It really deserves it, I think. Especially given that it doesn't have any
direct usage of `vm` package now.

pkg/compiler/compiler_test.go

@@ -0,0 +1,53 @@
+package compiler_test
+
+import (
+	"io/ioutil"
+	"os"
+	"path"
+	"testing"
+
+	"github.com/CityOfZion/neo-go/pkg/compiler"
+)
+
+const examplePath = "../../examples"
+
+func TestExamplesFolder(t *testing.T) {
+	infos, err := ioutil.ReadDir(examplePath)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for _, info := range infos {
+		infos, err := ioutil.ReadDir(path.Join(examplePath, info.Name()))
+		if err != nil {
+			t.Fatal(err)
+		}
+		if len(infos) == 0 {
+			t.Fatal("detected smart contract folder with no contract in it")
+		}
+
+		filename := filterFilename(infos)
+		targetPath := path.Join(examplePath, info.Name(), filename)
+		if err := compileFile(targetPath); err != nil {
+			t.Fatal(err)
+		}
+	}
+}
+
+func filterFilename(infos []os.FileInfo) string {
+	for _, info := range infos {
+		if !info.IsDir() {
+			return info.Name()
+		}
+	}
+	return ""
+}
+
+func compileFile(src string) error {
+	file, err := os.Open(src)
+	if err != nil {
+		return err
+	}
+	_, err = compiler.Compile(file)
+	return err
+}