Per language HOWTO's on writing functions (#208)

* fnctl: improve UX for howto's

* doc: go function howto

* fnctl: show the progress of build calls

* doc: php function howto

* doc: fix Go HOWTO

* doc: Node Functions HOWTO

* doc: Python Functions HOWTO

* doc: improve README files

* doc: ccirello -> USERNAME

* docs: fix Python example

Used an idiomatic method (isatty) to decide whether stdin must
be read or not.

* doc: fix go example

* fnctl: fix docker push output

docs/howto/go/hello.go

@@ -0,0 +1,17 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+)
+
+type Person struct {
+	Name string
+}
+
+func main() {
+	p := &Person{Name: "World"}
+	json.NewDecoder(os.Stdin).Decode(p)
+	fmt.Println("Hello", p.Name, "!!!")
+}