adds isInteractive and quit (#236)

Author: jmd-mongo

source/reference/methods.txt

@@ -827,6 +827,11 @@ Native Methods
 
      - Description
 
+   * - ``isInteractive()`` 
+
+     - Returns a boolean indicating whether mongosh is running in 
+       interactive or script mode.
+
    * - :manual:`load() </reference/method/load/>`
 
      - Loads and runs a JavaScript file in the shell.
@@ -854,6 +859,10 @@ Native Methods
           > print(x)
           example text
 
+   * - ``quit()``
+
+     - Exits the current shell session.
+
    * - ``sleep()``
 
      - Suspends the |mongo| shell for a given period of time.