Added processing instructions to JS object conversion

Author: oozcitak

src/XMLNode.coffee

@@ -46,6 +46,12 @@ module.exports = class XMLNode
           @attribute(attKey.substr(@stringify.convertAttKey.length), attVal)
           delete name[attKey]
 
+      # assign processing instructions and remove from this object
+      for own piKey, piVal of name
+        if @stringify.convertPIKey and piKey.indexOf(@stringify.convertPIKey) == 0
+          @instruction(piKey.substr(@stringify.convertPIKey.length), piVal)
+          delete name[piKey]
+
       # insert children
       for own key, val of name
 

src/XMLStringifier.coffee

@@ -59,6 +59,7 @@ module.exports = class XMLStringifier
 
   # strings to match while converting from JS objects
   convertAttKey: '@'
+  convertPIKey: '!'
   convertTextKey: '#text'
   convertCDataKey: '#cdata'
   convertCommentKey: '#comment'

test/object.coffee

@@ -60,6 +60,7 @@ vows
                     person:
                         name: "John"
                         '@age': 35
+                        '!pi': 'mypi'
                         '#comment': 'Good guy'
                         '#cdata': 'well formed!'
                         unescaped:
@@ -83,6 +84,7 @@ vows
             'resulting XML': (topic) ->
                 xml = '<root>' +
                           '<ele>simple element</ele>' +
+                          '<?pi mypi?>' +
                           '<person age="35">' +
                               '<name>John</name>' +
                               '<!-- Good guy -->' +