Fix spelling of instance.

Classes/BITCrashAttachment.h

@@ -50,7 +50,7 @@
  @param crashAttachmentData The attachment data as NSData
  @param contentType         The content type of your data as MIME type
  
- @return An instsance of BITCrashAttachment
+ @return An instance of BITCrashAttachment
  */
 - (instancetype)initWithFilename:(NSString *)filename
              crashAttachmentData:(NSData *)crashAttachmentData

Classes/BITFeedbackComposeViewController.h

@@ -35,7 +35,7 @@
  View controller allowing the user to write and send new feedback
  
  To add this view controller to your own app and push it onto a navigation stack,
- don't create the intance yourself, but use the following code to get a correct instance:
+ don't create the instance yourself, but use the following code to get a correct instance:
  
      [[BITHockeyManager sharedHockeyManager].feedbackManager feedbackComposeViewController]
  

Classes/BITFeedbackListViewController.h

@@ -44,7 +44,7 @@
  are allowed to be set.
  
  To add this view controller to your own app and push it onto a navigation stack,
- don't create the intance yourself, but use the following code to get a correct instance:
+ don't create the instance yourself, but use the following code to get a correct instance:
  
      [[BITHockeyManager sharedHockeyManager].feedbackManager feedbackListViewController:NO]