Add basic config mechanism

include/sardine.py

 import os
 import sys
 
+import yaml
+
 
 class PluginError(Exception):
     pass
     pass
 
 
+class ConfigError(Exception):
+
+    def __init__(self, path, key):
+        self.path = path
+        self.key = key
+
+    def __str__(self):
+        return "invalid key: %r in %s" % (self.key, self.path)
+
+
+class Config(object):
+
+    def __init__(self, paths, valid_keys):
+        self._valid_keys = valid_keys
+        for path in paths:
+            self.load(path)
+
+    def __str__(self):
+        ss = ["  %s: %s" % (vk, getattr(self, vk))
+              for vk in self._valid_keys]
+        return "\n".join(ss)
+
+    def load(self, path):
+        try:
+            with open(path) as fh:
+                conf = yaml.load(fh)
+        except IOError:
+            pass
+        else:
+            for key in conf.keys():
+                if key in self._valid_keys:
+                    setattr(self, key, conf[key])
+                else:
+                    raise ConfigError(path, key)
+
+
 class XGPRenderer(object):
 
     def __init__(self, txt=None):
 
     name = "sardine"
 
+    cfg_paths = [
+        '/etc/sardine/config',
+        '%(HOME)s/.config/sardine/config' % os.environ,
+        '.sardine.config'
+    ]
+
+    cfg_valid_keys = [
+    ]
+
     def __init__(self, cmdargs):
         self.cmdargs = cmdargs
         self._set_pluginpath()
+        self.config = Config(self.cfg_paths, self.cfg_valid_keys)
 
     def _set_pluginpath(self):
         mypath = os.path.dirname(os.path.realpath(sys.argv[0]))