be more tolerant with POST requests

POST request data was only being used if the request used the proper
MIME type (Flask probably wanted "application/json"). Now the code tries
out 3 ways of getting the data:

    1/ The request had the right MIME type. The data will be in
    the request.json object provided by Flask. This is the only scenario
    the code supported previously.

    2/ The request did not have a MIME type defined or had the wrong one
    (with the exception of HTML form MIME types, see 3/). The app will
    try to decode the JSON from request.data .

    3/ The request had the wrong MIME type defined - it said it was HTML
    form data, but it actually contained JSON where the HTML form data
    was supposed to be. The app will try to decode the JSON in
    request.form .
remove commented out unused route from /lookup
allow POST-ing to /lookup without trailing slash

fix #37