Unhandled exception in case of bad request fixed.
Unhandled exception in case of bad request fixed.

If we make request with wrong token we get unhandled exception because
X-Ratelimit-Remaining and X-Ratelimit-Limin headers are not set in
response.
Added checking for X-Ratelimit-Remaining and X-Ratelimit-Limit after
getting response from server.

3nGercog/InstaSharp,danielmundim/InstaSharp,crashdavis23/InstaSharp,InstaSharp/InstaSharp,danielmundim/InstaSharp,3nGercog/InstaSharp,crashdavis23/InstaSharp,theShiva/InstaSharp,theShiva/InstaSharp