Switched the check in order to allow users to override the blacklist, if they wish to.
Only add the query string if it's not empty and it's not equal to '?'
Merge pull request #419 from orientalsensation/RetryHandlerFix

Switched the check in order to allow users to override the blacklist, if they wish to.
Merge pull request #420 from orientalsensation/getUrlWithQueryString

Only add the query string if it's not empty and it's not equal to '?'
Merge branch 'master' of https://github.com/loopj/android-async-http

# By Oriental Sensation
# Via Marek Sebera (2) and Oriental Sensation (1)
* 'master' of https://github.com/loopj/android-async-http:
  Only add the query string if it's not empty and it's not equal to '?'
  Switched the check in order to allow users to override the blacklist, if they wish to.