The default transport was changed in commit 0d66f2c6 and the proxy feature was forgotten.

- https://golang.org/src/net/http/transport.go#L43
- https://golang.org/pkg/net/http/#ProxyFromEnvironment

Reducing these values avoid going over the max number of file descriptors when refreshing lot of feeds

- Make sure query strings parameters are encoded
- As opposed to the standard library, do not append equal sign
for query parameters with empty value
- Strip URL fragments like Web browsers

- Feeds with charset specified only in Content-Type header and not in XML document
- Feeds with charset specified in both places
- Feeds with charset specified only in XML document and not in HTTP header