Fix typos and warnings for GoReport / GolangCiLinter (#132)

- typos
- gofmt -s
- govet warnings
- golangci-lint run

pkg/vm/stack.go

@@ -33,7 +33,7 @@ type Element struct {
 	stack      *Stack
 }
 
-// NewElement returns a new Element object, with its underlying value infered
+// NewElement returns a new Element object, with its underlying value inferred
 // to the corresponding type.
 func NewElement(v interface{}) *Element {
 	return &Element{