title: The toJSON(fromJSON('1.json')) in rjsonlite does not produce the same JSON
body: <p>I was trying to use jsonlite to work with my JSON requests. I was expecting that applying toJSON() to the result of fromJSON() and writing it to a file will produce the same JSON as the original. Apparently, fromJSON does a lot of type conversion from numeric to character and encloses single values into []. </p>
  
  <p>Are there any parameters I can use to make sure we obtain the same json file by toJSON(fromJSON) or I have to care about all the types of all elements myself. </p>
  
  <p>Maybe this could be achieved by some other R JSON library. </p>
  
  <p>Here is the sample of original JSON and past transformation. </p>
  
  <p>Original:</p>
  
  <pre><code>"target": "LENGTH",
  "solvers_list": "TMtmil",   "passes_num": 45
  </code></pre>
  
  <p>Modified: </p>
  
  <pre><code>"target":["LENGTH"],"solvers_list":["TMtmil"],"passes_num":[45]
  </code></pre>