gistfile1.m

+ (Response *)get:(NSString *)url withUser:(NSString *)user andPassword:(NSString *)password {
	NSMutableURLRequest *request = [NSMutableURLRequest requestWithUrl:[NSURL URLWithString:url] andMethod:@"GET"];
	return [self sendRequest:request withUser:user andPassword:password];
}

// to:

+ (Response *)get:(NSString *)url withUser:(NSString *)user andPassword:(NSString *)password {
	NSMutableURLRequest *request = [NSMutableURLRequest requestWithUrl:[NSURL URLWithString:url] andMethod:@"GET"];
	for (NSDictionary *header in requestHeaders)
		[request addValue:[header objectForKey:@"value"] forHTTPHeaderField:[header objectForKey:@"name"]];
	return [self sendRequest:request withUser:user andPassword:password];
}

-[NSURLRequest setAllHTTPHeaderFields:] saves you the for loop.

At the expense of overwriting existing headers, such as any previously set "Accepts" header, but this may be OK for what you are doing.