fix typos and modify explanation

Author: tungen

libact/base/interfaces.py

@@ -59,7 +59,7 @@ def label(self, feature):
     
         Parameters
         ----------
-        feautre : array-like, shape (n_features,)
+        feature : array-like, shape (n_features,)
             The feature vector whose label is to queried.
             
         Returns

libact/labelers/ideal_labeler.py

@@ -13,7 +13,7 @@ class IdealLabeler(Labeler):
     Parameters
     ----------
     dataset: Dataset object
-        Dataset object with the ground truth in labeled data.
+        Dataset object with the ground-truth label for each sample.
         
     """