Feature post photo as nsdata

Typically developers have access to UIImage objects and want to share them to Tumblr, it doesn't make sense to store them and then share them.

This change added support for sharing Images from NSData objects instead of files.


Sample Request

```objective-c

UIImage* image = ....
NSString* blogName = ....

NSData* imageData  = UIImageJPEGRepresentation(image, 1);
NSDictionary* parameters   = @{@"caption": @"caption text"};
NSArray* fileNameArray  = @["image.jpg"];
NSArray* imageDataArray = @[imageData];

 [[TMAPIClient sharedInstance] photo:blogName imageNSDataArray:imageDataArray contentTypeArray:contentTypeArray fileNameArray:fileNameArray parameters:parameters callback:^(id response, NSError *error) {
        [_shareItems.sharePanel didShareToPlatform:self withError:error];
           if (error)
               NSLog(@"error: %@", error);
        
    }];


```