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.

React/Base/RCTFPSGraph.m

@@ -9,6 +9,7 @@
 
 #import "RCTFPSGraph.h"
 
+#import "RCTAssert.h"
 #import "RCTDefines.h"
 
 #if RCT_DEV
@@ -32,7 +33,7 @@
 
 - (instancetype)initWithFrame:(CGRect)frame graphPosition:(RCTFPSGraphPosition)position name:(NSString *)name color:(UIColor *)color
 {
-  if (self = [super initWithFrame:frame]) {
+  if ((self = [super initWithFrame:frame])) {
     _margin = 2;
     _prevTime = -1;
     _maxFPS = 0;
@@ -42,8 +43,10 @@
     _frames = malloc(sizeof(float) * _length);
     memset(_frames, 0, sizeof(float) * _length);
 
-    _name = name;
-    _position = position;
+    _name = name ?: @"FPS";
+    _position = position ?: RCTFPSGraphPositionLeft;
+
+    color = color ?: [UIColor greenColor];
     _graph = [self createGraph:color];
     _label = [self createLabel:color];
 
@@ -53,6 +56,9 @@
   return self;
 }
 
+RCT_NOT_IMPLEMENTED(-initWithFrame:(CGRect)frame)
+RCT_NOT_IMPLEMENTED(-initWithCoder:(NSCoder *)aDecoder)
+
 - (void)dealloc
 {
   free(_frames);