Started writing documentation and adding examples

exec.go

@@ -5,10 +5,16 @@ import (
 	"os"
 )
 
+// Runnable is a pipeline that can be executed by Run. The *script.Pipe type implements this interface
 type Runnable interface {
+	// Stdout invokes the runnable task with the result written to stdout, if successful.  It returns the number
+	// of bytes written out, or an error if the task was unsuccessful.
 	Stdout() (int, error)
 }
 
+// Run takes a number of pipes and executes them in order, until they all succeed or the first error is encountered.
+// If a runnable task fails with an error, it will write the error to stderr and terminate the program with exit code 1.
+// It's designed to be used within the "main()" function.
 func Run(pipes ...Runnable) {
 	for _, pipe := range pipes {
 		if _, err := pipe.Stdout(); err != nil {