Fix unit tests for Xcode 8.3 (#608)

* Changed the NSTimer to a dispatch_timer.  NSTimers only fire in certain run modes.
* Added environment parameters to control the test cases without re-compiling.
* Standardized test cases.
* All tests pass.

Author: E-B-Smith

Branch-SDK/Branch-SDK/BNCServerRequestQueue.h

@@ -6,13 +6,12 @@
 //
 //
 
-#import "BNCServerRequest.h"
 
+#import "BNCServerRequest.h"
 @class BranchOpenRequest;
 
-@interface BNCServerRequestQueue : NSObject
 
-@property (nonatomic, readonly) unsigned int size;
+@interface BNCServerRequestQueue : NSObject
 
 - (void)enqueue:(BNCServerRequest *)request;
 - (BNCServerRequest *)dequeue;
@@ -32,4 +31,6 @@
 
 + (id)getInstance;
 
+@property (readonly, assign) NSInteger queueDepth;
+@property (readonly, assign) BOOL isDirty;
 @end