Increased warning levels to -Wall -Wextra, and fixed Xcode 7 beta issues

Summary:
@public

I've increased the warning levels in the OSS frameworks, which caught a bunch of minor issues. I also fixed some new errors in Xcode 7 relating to designated initializers and TLS security.

Test Plan:
* Test the sample apps and make sure they still work.
* Run tests.

Libraries/Network/RCTDataManager.m

@@ -164,6 +164,10 @@ typedef void (^RCTDataLoaderCallback)(NSData *data, NSString *MIMEType, NSError
                         handler:(id<RCTURLRequestHandler>)handler
                        callback:(RCTDataLoaderCallback)callback
 {
+   RCTAssertParam(request);
+   RCTAssertParam(handler);
+   RCTAssertParam(callback);
+
   if ((self = [super init])) {
     _callback = callback;
     _request = [[RCTActiveURLRequest alloc] init];
@@ -175,6 +179,11 @@ typedef void (^RCTDataLoaderCallback)(NSData *data, NSString *MIMEType, NSError
   return self;
 }
 
+- (instancetype)init
+{
+  return [self initWithRequest:nil handler:nil callback:nil];
+}
+
 - (void)URLRequest:(id)requestToken didReceiveResponse:(NSURLResponse *)response
 {
   RCTAssert([requestToken isEqual:_requestToken], @"Shouldn't ever happen");

Libraries/Network/RCTNetwork.xcodeproj/project.pbxproj

@@ -162,6 +162,7 @@
 				GCC_SYMBOLS_PRIVATE_EXTERN = NO;
 				GCC_WARN_64_TO_32_BIT_CONVERSION = YES;
 				GCC_WARN_ABOUT_RETURN_TYPE = YES_ERROR;
+				GCC_WARN_INITIALIZER_NOT_FULLY_BRACKETED = YES;
 				GCC_WARN_UNDECLARED_SELECTOR = YES;
 				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
 				GCC_WARN_UNUSED_FUNCTION = YES;
@@ -170,6 +171,10 @@
 				MTL_ENABLE_DEBUG_INFO = YES;
 				ONLY_ACTIVE_ARCH = YES;
 				SDKROOT = iphoneos;
+				WARNING_CFLAGS = (
+					"-Werror",
+					"-Wall",
+				);
 			};
 			name = Debug;
 		};
@@ -196,6 +201,7 @@
 				GCC_C_LANGUAGE_STANDARD = gnu99;
 				GCC_WARN_64_TO_32_BIT_CONVERSION = YES;
 				GCC_WARN_ABOUT_RETURN_TYPE = YES_ERROR;
+				GCC_WARN_INITIALIZER_NOT_FULLY_BRACKETED = YES;
 				GCC_WARN_UNDECLARED_SELECTOR = YES;
 				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
 				GCC_WARN_UNUSED_FUNCTION = YES;
@@ -204,6 +210,10 @@
 				MTL_ENABLE_DEBUG_INFO = NO;
 				SDKROOT = iphoneos;
 				VALIDATE_PRODUCT = YES;
+				WARNING_CFLAGS = (
+					"-Werror",
+					"-Wall",
+				);
 			};
 			name = Release;
 		};

Libraries/Network/RCTReachability.m

@@ -9,6 +9,7 @@
 
 #import "RCTReachability.h"
 
+#import "RCTAssert.h"
 #import "RCTBridge.h"
 #import "RCTEventDispatcher.h"
 
@@ -59,9 +60,12 @@ static void RCTReachabilityCallback(__unused SCNetworkReachabilityRef target, SC
 
 - (instancetype)initWithHost:(NSString *)host
 {
+  RCTAssertParam(host);
+  RCTAssert(![host hasPrefix:@"http"], @"Host value should just contain the domain, not the URL scheme.");
+
   if ((self = [super init])) {
     _status = RCTReachabilityStateUnknown;
-    _reachability = SCNetworkReachabilityCreateWithName(kCFAllocatorDefault, [host UTF8String]);
+    _reachability = SCNetworkReachabilityCreateWithName(kCFAllocatorDefault, host.UTF8String);
     SCNetworkReachabilityContext context = { 0, ( __bridge void *)self, NULL, NULL, NULL };
     SCNetworkReachabilitySetCallback(_reachability, RCTReachabilityCallback, &context);
     SCNetworkReachabilityScheduleWithRunLoop(_reachability, CFRunLoopGetMain(), kCFRunLoopCommonModes);