Added __reduce__() and __setstate__() methods to database classes.

These methods are needed in order to be able to properly pickle and unpickle
the database. Note that these classes - ThermoDatabase, KineticsDatabase,
and StatmechDatabase - need to be new-style classes (i.e. derived from
object) for __reduce__() and __setstate__() to be used by the pickler.

Closes #103.

rmgpy/data/kinetics.py

@@ -3417,7 +3417,7 @@ def filterReactions(reactants, products, reactionList):
     return reactions
 
 ###########
-class KineticsDatabase:
+class KineticsDatabase(object):
     """
     A class for working with the RMG kinetics database.
     """
@@ -3441,6 +3441,25 @@ def __init__(self):
         }
         self.global_context = {}
 
+    def __reduce__(self):
+        """
+        A helper function used when pickling a KineticsDatabase object.
+        """
+        d = {
+            'families': self.families,
+            'libraries': self.libraries,
+            'libraryOrder': self.libraryOrder,
+        }
+        return (KineticsDatabase, (), d)
+
+    def __setstate__(self, d):
+        """
+        A helper function used when unpickling a KineticsDatabase object.
+        """
+        self.families = d['families']
+        self.libraries = d['libraries']
+        self.libraryOrder = d['libraryOrder']
+
     def load(self, path, families=None, libraries=None, depositories=None):
         """
         Load the kinetics database from the given `path` on disk, where `path`

rmgpy/data/statmech.py

@@ -421,7 +421,7 @@ def getStatmechData(self, molecule, thermoModel):
 
 ################################################################################
 
-class StatmechDatabase:
+class StatmechDatabase(object):
     """
     A class for working with the RMG statistical mechanics (frequencies) database.
     """
@@ -441,6 +441,27 @@ def __init__(self):
         }
         self.global_context = {}
 
+    def __reduce__(self):
+        """
+        A helper function used when pickling a StatmechDatabase object.
+        """
+        d = {
+            'depository': self.depository,
+            'libraries': self.libraries,
+            'groups': self.groups,
+            'libraryOrder': self.libraryOrder,
+        }
+        return (StatmechDatabase, (), d)
+
+    def __setstate__(self, d):
+        """
+        A helper function used when unpickling a StatmechDatabase object.
+        """
+        self.depository = d['depository']
+        self.libraries = d['libraries']
+        self.groups = d['groups']
+        self.libraryOrder = d['libraryOrder']
+
     def load(self, path, libraries=None, depository=True):
         """
         Load the statmech database from the given `path` on disk, where `path`

rmgpy/data/thermo.py

@@ -315,7 +315,7 @@ def processOldLibraryEntry(self, data):
 
 ################################################################################
 
-class ThermoDatabase:
+class ThermoDatabase(object):
     """
     A class for working with the RMG thermodynamics database.
     """
@@ -333,6 +333,27 @@ def __init__(self):
         }
         self.global_context = {}
 
+    def __reduce__(self):
+        """
+        A helper function used when pickling a ThermoDatabase object.
+        """
+        d = {
+            'depository': self.depository,
+            'libraries': self.libraries,
+            'groups': self.groups,
+            'libraryOrder': self.libraryOrder,
+        }
+        return (ThermoDatabase, (), d)
+
+    def __setstate__(self, d):
+        """
+        A helper function used when unpickling a ThermoDatabase object.
+        """
+        self.depository = d['depository']
+        self.libraries = d['libraries']
+        self.groups = d['groups']
+        self.libraryOrder = d['libraryOrder']
+
     def load(self, path, libraries=None, depository=True):
         """
         Load the thermo database from the given `path` on disk, where `path`