Check for multiline shebang script hacks

Fixes #8

test/fixtures/script.rkt

@@ -0,0 +1,7 @@
+#!/bin/sh
+#| -*- scheme -*-
+exec racket -um "$0" "$@"
+|#
+
+(require racket/file racket/path racket/list racket/string
+         (for-syntax racket/base))

test/fixtures/script.scala

@@ -0,0 +1,9 @@
+#!/bin/sh
+exec scala "$0" "$@"
+!#
+
+object HelloWorld {
+  def main(args: Array[String]) {
+    println("Hello, world!")
+  }
+}