Fix Xcode warnings on building (#235)

* Modified Issue_Template to be more descriptive

* Some minor changes to decription field

* Improved messages to make intention of creating different apps for different platforms more clear

Due to multiple requests in discord chanel, microsoft/react-native-code-push#723, microsoft/react-native-code-push#717

* FIxed spelling for Readme

* Supress XCode warnings on build

See #218 for details

src/ios/CodePushReportingManager.m

@@ -1,6 +1,8 @@
 #import "CodePushReportingManager.h"
 #import "StatusReport.h"
 
+#pragma GCC diagnostic ignored "-Wundeclared-selector"
+
 @implementation CodePushReportingManager
 
 int HasFailedReport = -1; // -1 = unset, 0 = false, 1 = true

src/ios/InstallOptions.m

@@ -12,7 +12,7 @@ -(void)encodeWithCoder:(NSCoder*)encoder {
 
 -(id)initWithCoder:(NSCoder*)decoder {    
     self.installMode = [decoder decodeIntegerForKey:InstallModeKey];
-    self.minimumBackgroundDuration = [decoder decodeIntegerForKey:MinimumBackgroundDurationKey];
+    self.minimumBackgroundDuration = (int)[decoder decodeIntegerForKey:MinimumBackgroundDurationKey];
     return self;
 }
 

src/ios/UpdateHashUtils.m

@@ -63,7 +63,7 @@ + (NSString*)computeFinalHashFromManifestEntries:(NSMutableArray*)manifest
 + (NSString*)computeHashForData:(NSData*)inputData
 {
     uint8_t digest[CC_SHA256_DIGEST_LENGTH];
-    CC_SHA256(inputData.bytes, inputData.length, digest);
+    CC_SHA256(inputData.bytes, (CC_LONG)inputData.length, digest);
     NSMutableString* inputHash = [NSMutableString stringWithCapacity:CC_SHA256_DIGEST_LENGTH * 2];
     for (int i = 0; i < CC_SHA256_DIGEST_LENGTH; i++) {
         [inputHash appendFormat:@"%02x", digest[i]];