Description:
------------
Line 687 of oauth.c has an "if" on the "urlparts" variable, 
but if that "if" is false then the result is not gracefully 
handled.  Specifically, making a request to 
"http://server.local" causes an error "Invalid protected 
resource url, unable to generate signature base string" but 
it would be more useful to say that the path part of the URL 
is missing (ie "http://server.local/" with the trailing slash 
works).

Reproduce code:
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$oauth = new OAuth($config['consumer_key'], $config['consumer_secret']);
$oauth->setToken($oauth_token, $oauth_token_secret);
$result = $oauth->fetch("http://server.local", null, OAUTH_HTTP_METHOD_GET);


Expected result:
----------------
An error about the missing path on the URL (or even for it to 
add the / to the end of the URL like what curl does)

Actual result:
--------------
Invalid protected resource url, unable to generate signature 
base string