Add cutoff parameter to build_dict.

Author: sharannarang

python/paddle/v2/dataset/imdb.py

@@ -124,15 +124,15 @@ def test(word_idx):
         re.compile("aclImdb/test/neg/.*\.txt$"), word_idx)
 
 
-def word_dict():
+def word_dict(cutoff=150):
     """
     Build a word dictionary from the corpus.
 
     :return: Word dictionary
     :rtype: dict
     """
     return build_dict(
-        re.compile("aclImdb/((train)|(test))/((pos)|(neg))/.*\.txt$"), 150)
+        re.compile("aclImdb/((train)|(test))/((pos)|(neg))/.*\.txt$"), cutoff)
 
 
 def fetch():