Images broken after WP update !

I don’t remember which version of WP I had earlier. It was 3.5.x. I updated my WP to 3.6 from admin portal and now all my images are broken.

I checked in posts, the image link is correct. but HTML in publish it is entirely different.

mark up in my post :
<a href="https://i.imgur.com/yxxza.jpg"><img class="alignnone" title="gestures" src="https://i.imgur.com/yxxza.jpg" alt="" width="958" height="268" /></a>

mark up in published post (got this from view source in Chrome) :
<a href="https://i2.wp.com/i.imgur.com/yxxza.jpg"><img class="alignnone" title="gestures" src="https://i2.wp.com/i.imgur.com/yxxza.jpg?resize=510%2C143" alt="" data-recalc-dims="1" /></a></p>

I am not understanding why wordpress is adding i2.wp.com something