Grok credentials from .netrc if unspecified

The constructor tries to grok the authentication credentials from the
.netrc file using Net::Netrc if the PASSWORD argument is indefined.

Signed-off-by: Gustavo L. de M. Chaves <gnustavo@cpan.org>
Drop requirement of HTTP::Status

Now the module is required inside an eval block. If it cannot be
required the error message simply goes without the code string.

Signed-off-by: Gustavo L. de M. Chaves <gnustavo@cpan.org>
Make dzil infer requirements and recommendations

Signed-off-by: Gustavo L. de M. Chaves <gnustavo@cpan.org>