Best reco hits events

This addresses issues #22 (closed) and #24 (closed)

This is ready for merge into master. Although I am not sure I understand why the code style fails here on git (I updated yapf on my computer and used it to correct the code style but maybe I am missing a detail here?).

km3io/offline.py

@@ -143,9 +143,9 @@ class OfflineKeys:
             except those found in fake branches.
         """
         if self._mc_tracks_keys is None:
-            fake_branches = set([
-                'mc_trks.usr_data', 'mc_trks.usr', 'mc_trks.usr_names'
-            ])  # same solution as above can be used
+            fake_branches = set(
+                ['mc_trks.usr_data', 'mc_trks.usr',
+                 'mc_trks.usr_names'])  # same solution as above can be used
             tree = uproot.open(self._file_path)['E']['Evt']['mc_trks']
             self._mc_tracks_keys = [
                 key.decode('utf8') for key in tree.keys()
@@ -334,7+334,7 @@
             OfflineKeys.
         """
         if self._keys is None:
             self._keys = OfflineKeys(self._file_path)
         return self._keys
 
 
@@ -568,7+568,7 @@
                     str(stages)))
         else:
             fit_data = np.array([
-                i[k]
-                for i, j, k in zip(fit_info, rec_stages[:, 0], rec_stages[:,
-                                                                          1])
-                if k is not None
+                i[k] for i, j, k in zip(fit_info, rec_stages[:, 0],
+                                        rec_stages[:, 1]) if k is not None
             ])
             rec_array = np.core.records.fromarrays(fit_data.transpose(),
                                                    names=keys)