sbang support: add node-js and fix lua

This adds sbang hook support for node-js and fixes the sbang filter
for lua (the character class exclusion was swallowing newlines and
reporting a false positive if lua was mentioned anywhere in the 
file).

bin/sbang

@@ -104,6 +104,8 @@ lines=0
 while read line && ((lines < 2)) ; do
     if [[ "$line" = '#!'* ]]; then
         interpreter="${line#\#!}"
+    elif [[ "$line" = '//!'*node* ]]; then
+        interpreter="${line#//!}"
     elif [[ "$line" = '--!'*lua* ]]; then
         interpreter="${line#--!}"
     fi