[firefox]: bugfix options_page

[zloidemon]

diff -ruN kango.orig/changelog.txt kango/changelog.txt
--- kango.orig/changelog.txt    2016-01-09 23:39:02.000000000 +0300
+++ kango/changelog.txt 2016-01-18 17:12:50.340036223 +0300
@@ -1,6 +1,9 @@
 Kango framework changelog
 =========================

+Version 1.8.1
+- Firefox: Fix "options_page"
+
 Version 1.8.0
 -------------
 - Firefox: Electrolysis compatibility
diff -ruN kango.orig/kango/builders/firefox.py kango/kango/builders/firefox.py
--- kango.orig/kango/builders/firefox.py    2016-01-09 23:39:02.000000000 +0300
+++ kango/kango/builders/firefox.py 2016-01-18 16:48:35.602136176 +0300
@@ -21,7 +21,8 @@
         'em:version': 'version',
         'em:creator': 'creator',
         'em:homepageURL': 'homepage_url',
-        'em:updateURL': 'update_url'
+        'em:updateURL': 'update_url',
+        'em:optionsURL': 'options_page'
     }

     def __init__(self, info, kango_path):
@@ -66,6 +67,9 @@
         for key in self._transform_table:
             elem = description.getElementsByTagName(key)[0]
             info_val = getattr(self._info, self._transform_table[key], '')
+            if key == 'em:optionsURL':
+                info_val = "chrome://{product}/content/{file}".format(
+                    product=KEYWORDS['product'], file=info_val)
             if info_val != '':
                 elem.childNodes[0].data = info_val
             else: