title: SparkR says it can't find function read.df
body: <p>Just what the title says. Every time I fire up the SparkR shell on the RedHat machine I'm using and try to use the function read.df(), it says that it could not find that function. I'm using SparkR 2.0, if that helps. </p>
  
  <p>To be more specific, here's what I tried to type:</p>
  
  <p><code>data &lt;- read.df(sqlContext, "/path/to/the/file", "parquet")</code></p>
  
  <p><strong>Edit:</strong> To clarify, here is the exact situation:</p>
  
  <p><code>&gt; data &lt;- df.read("valid/path/to/parquet/file", "parquet") 
  Error: could not find function "df.read"</code></p>