Fix minor errors

* Extra Notes heading in docstring
* Typo in docstring

Author: mdpiper

bmi/info.py

@@ -1,5 +1,5 @@
 #! /usr/bin/env python
-"""Interface that describes a model and it's input and output variables."""
+"""Interface that describes a model and its input and output variables."""
 
 
 class BmiInfo(object):

bmi/time.py

@@ -91,15 +91,13 @@ def get_time_step(self):
     def get_time_units(self):
         """Time units of the model.
 
+        CSDMS uses the UDUNITS standard from Unidata.
+
         Returns
         -------
         float
           The model time unit; e.g., `days` or `s`.
 
-        Notes
-        -----
-        CSDMS uses the UDUNITS standard from Unidata.
-
         Notes
         -----
         .. code-block:: c