CheckstyleBear: Load google and sun rules from jar

The google and sun rules are provided in the jar,
and those rules are known to be compatible with the jar version.

Fixes coala#1017
Fixes coala#1034

bears/java/CheckstyleBear.py

@@ -2,13 +2,20 @@
 from coalib.settings.Setting import path
 
 
-known_checkstyles = {
+_checkstyle_provided_styles = {
+    # google: since version 6.9
     "google": "https://raw.githubusercontent.com/checkstyle/checkstyle/master/src/main/resources/google_checks.xml",
     "sun": 'https://raw.githubusercontent.com/checkstyle/checkstyle/master/src/main/resources/sun_checks.xml',
+}
+
+_online_styles = {
     "android-check-easy": "https://raw.githubusercontent.com/noveogroup/android-check/master/android-check-plugin/src/main/resources/checkstyle/checkstyle-easy.xml",
     "android-check-hard": "https://raw.githubusercontent.com/noveogroup/android-check/master/android-check-plugin/src/main/resources/checkstyle/checkstyle-hard.xml",
     "geosoft": "http://geosoft.no/development/geosoft_checks.xml"}
 
+# To be deprecated
+known_checkstyles = dict(_checkstyle_provided_styles, **_online_styles)
+
 
 def check_invalid_configuration(checkstyle_configs, use_spaces, indent_size):
     if (checkstyle_configs is 'google' and
@@ -75,10 +82,14 @@ def create_arguments(
         check_invalid_configuration(
             checkstyle_configs, use_spaces, indent_size)
 
-        if checkstyle_configs in known_checkstyles:
+        if checkstyle_configs in _online_styles:
             checkstyle_configs = self.download_cached_file(
-                known_checkstyles[checkstyle_configs],
+                _online_styles[checkstyle_configs],
                 checkstyle_configs + ".xml")
+        elif checkstyle_configs in _checkstyle_provided_styles:
+            # Locate the file as an absolute resource in the jar
+            url = _checkstyle_provided_styles[checkstyle_configs]
+            checkstyle_configs = url[url.rfind('/'):]
 
         return ('-jar', self.checkstyle_jar_file, '-c',
                 checkstyle_configs, filename)