docs: Add some documentation about #!

Add the #! syntax to the quickstart guide, and to the tutorial as well.
Fixes #992.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>

docs/quickstart.rst

@@ -31,13 +31,18 @@ Quickstart
 
 7. Open up an elite programming editor and type::
 
+       #! /usr/bin/env hy
        (print "I was going to code in Python syntax, but then I got Hy.")
 
 8. Save as ``awesome.hy``.
-9. And run your first Hy program::
+9. Make it executable::
 
-        hy awesome.hy
+        chmod +x awesome.hy
 
-10. Take a deep breath so as to not hyperventilate.
-11. Smile villainously and sneak off to your hydeaway and do
+10. And run your first Hy program::
+
+        ./awesome.hy
+
+11. Take a deep breath so as to not hyperventilate.
+12. Smile villainously and sneak off to your hydeaway and do
     unspeakable things.

docs/tutorial.rst

@@ -306,6 +306,13 @@ Comments start with semicolons:
   ; (print "but this will not")
   (+ 1 2 3)  ; we'll execute the addition, but not this comment!
 
+Hashbang (``#!``) syntax is supported:
+
+.. code-block:: clj
+
+   #! /usr/bin/env hy
+   (print "Make me executable, and run me!")
+
 Looping is not hard but has a kind of special structure.  In Python,
 we might do::