Added JSON output

[timoles]

I added a flag for JSON output to the tool. With the flag set it saves a JSON string instead of the traditional meg output.

I played/tested arround a bit and it should be stable (tbh I didn't test output created with --rawhttp).

The JSON structure:

{
   "request":{
      "url":"",
      "hostname":"",
      "method":"",
      "path":"",
      "host":"",
      "headers":[{
         "headerkey":"",
         "headervalue":""}],
      "body":"",
      "follow":false
   },
   "response":{
      "statuscode":,
      "status":"",
      "headers":[{
         "headerkey":"",
         "headervalue":""}],
      "body":""
   }
}

Not much more to say about it, I guess.