Description:
------------
OAuthProvider requires the request parameters oauth_nonce and oauth_timestamp even if the signature method is PLAINTEXT. You will get the following exception when one of the parameters is missing:

> Uncaught exception 'OAuthException' with message 'Missing required parameters'

RFC 5849 section 3.1[1] says the contrary:

oauth_timestamp
 The timestamp value as defined in Section 3.3.  The parameter
 MAY be omitted when using the "PLAINTEXT" signature method.

oauth_nonce
 The nonce value as defined in Section 3.3.  The parameter MAY
 be omitted when using the "PLAINTEXT" signature method.

[1] http://tools.ietf.org/html/rfc5849#section-3.1

The attached test script demonstrates the problem. When oauth_nonce and oauth_timestamp are re-added to the params array, all is fine. If they are removed, OAuthProvider throws an exception - which it should not


Test script:
---------------
<?php
$params = array(
    'oauth_consumer_key' => 'anyone',
    'oauth_callback'     => 'http://example.org/',
    'oauth_signature_method' => 'PLAINTEXT',
    'oauth_signature' => 'secret&',
    //'oauth_nonce' => '',
    //'oauth_timestamp' => '',
);
function allfine()
{
    return OAUTH_OK;
}
function lookupConsumer($prov)
{
    $prov->consumer_secret = 'secret';
    return OAUTH_OK;
}
$prov = new OAuthProvider($params);
$prov->isRequestTokenEndpoint(true);
$prov->consumerHandler('lookupConsumer');
$prov->timestampNonceHandler('allfine');
$prov->tokenHandler('allfine');
$prov->checkOAuthRequest('http://example.com/', 'POST');
//no exception here
?>