title: syntaxnet demo.sh hangs when i use text file input
body: <p>I am trying to use SyntaxNet's demo.sh to tag and parse my own file. Similar to the instructions on <a href="https://github.com/tensorflow/models/tree/master/syntaxnet" rel="nofollow noreferrer">https://github.com/tensorflow/models/tree/master/syntaxnet</a> , I added to the context file:</p>
  
  <p>input {</p>
  
  <pre><code>name: 'my_input'
      record_format: 'english-text'
  Part {
      file_pattern: './input.txt'
  }
  </code></pre>
  
  <p>}</p>
  
  <p>input {</p>
  
  <pre><code>name: 'my_output'
  record_format: 'conll-sentence'
  Part {
      file_pattern: './output.conll'
  }
  </code></pre>
  
  <p>}</p>
  
  <p>and then ran ./syntaxnet/demo.sh --input=my_input --output=my_output. However, the code hangs after getting the term frequencies. The issue is similar to <a href="https://github.com/tensorflow/models/issues/208" rel="nofollow noreferrer">https://github.com/tensorflow/models/issues/208</a></p>