title: Pyarrow keeps converting string to binary using Pandas
body: <p>I am trying to convert a csv file to parquet using pandas and pyarrow in python2.7. </p>
  
  <p>I am having an issue with converting string to string from the pa.Table.from_pandas(df) conversion. It keeps converting the data type to 'binary' and this makes AWS Glue very unhappy.</p>
  
  <p>I have attempted a customized schema it will not work. </p>
  
  <pre><code>fields = []
  for name, type in dtypes.items():
          fields.append(pa.field(name, type))
  my_schema = pa.schema(fields)
  df = pd.read_csv(StringIO(file), delimiter="\t")
  table = pa.Table.from_pandas(df)
  </code></pre>
  
  <p>Previously was specifying the datatype when reading in the csv, that did not work either. Also tried replace_schema_metadata() but that doesn't do much as it isn't the actual schema.</p>