fn: rename from fnctl (#321)

* fn: rename from fnctl

* fn: predicting the release version for installer

* fn: predicting the release version for installer

fn/langs/base.go

@@ -0,0 +1,23 @@
+package langs
+
+import "fmt"
+
+// GetLangHelper returns a LangHelper for the passed in language
+func GetLangHelper(lang string) (LangHelper, error) {
+	switch lang {
+	case "go":
+		return &GoLangHelper{}, nil
+	case "node":
+		return &NodeLangHelper{}, nil
+	case "ruby":
+		return &RubyLangHelper{}, nil
+	}
+	return nil, fmt.Errorf("No language helper found for %v", lang)
+}
+
+type LangHelper interface {
+	Entrypoint() string
+	HasPreBuild() bool
+	PreBuild() error
+	AfterBuild() error
+}