Calculate weechat home using string_eval_path_home.

Using different path for the weechat configuration results in inability
to find right replacemenet_map json file. Fix it by using
string_eval_path_home method, which will return right weechat config
directory.

test_replacer.py

@@ -66,6 +66,9 @@ class Weechat(object):
     def _set_position(self, val):
         self.position = val
 
+    def string_eval_path_home(self, path, pointers, extra_vars, options):
+        return path
+
 
 weechat = Weechat()
 sys.modules['weechat'] = weechat