Xcode error: "_main", referenced from: implicit entry/start for main executable

Sorry, I am fairly new to iOS. I am getting the following error, which seems to be coming from something in the bottom to do with "_main".

Ld /Users/jianglin/Library/Developer/Xcode/DerivedData/TownHall_iPhone-bdlgipvgaapgjhglhromfvcubbxz/Build/Products/Debug-iphonesimulator/TownHall\ iPhone.app/TownHall\ iPhone normal i386
    cd "/Users/jianglin/Desktop/TownHall iPhone"
    export IPHONEOS_DEPLOYMENT_TARGET=8.1
    export PATH="/Applications/http://ift.tt/1eHqHUg"
    /Applications/http://ift.tt/1jmLxI7 -arch i386 -isysroot /Applications/http://ift.tt/1wvrkVu -L/Users/jianglin/Library/Developer/Xcode/DerivedData/TownHall_iPhone-bdlgipvgaapgjhglhromfvcubbxz/Build/Products/Debug-iphonesimulator -F/Users/jianglin/Library/Developer/Xcode/DerivedData/TownHall_iPhone-bdlgipvgaapgjhglhromfvcubbxz/Build/Products/Debug-iphonesimulator -filelist /Users/jianglin/Library/Developer/Xcode/DerivedData/TownHall_iPhone-bdlgipvgaapgjhglhromfvcubbxz/Build/Intermediates/TownHall\ iPhone.build/Debug-iphonesimulator/TownHall\ iPhone.build/Objects-normal/i386/TownHall\ iPhone.LinkFileList -Xlinker -rpath -Xlinker @executable_path/Frameworks -Xlinker -objc_abi_version -Xlinker 2 -ObjC -lPods-AFNetworking -lPods-Masonry -lPods-SDWebImage -framework CoreGraphics -framework Foundation -framework ImageIO -framework MobileCoreServices -framework Security -framework SystemConfiguration -framework UIKit -fobjc-arc -fobjc-link-runtime -Xlinker -no_implicit_dylibs -mios-simulator-version-min=8.1 -lPods -Xlinker -dependency_info -Xlinker /Users/jianglin/Library/Developer/Xcode/DerivedData/TownHall_iPhone-bdlgipvgaapgjhglhromfvcubbxz/Build/Intermediates/TownHall\ iPhone.build/Debug-iphonesimulator/TownHall\ iPhone.build/Objects-normal/i386/TownHall\ iPhone_dependency_info.dat -o /Users/jianglin/Library/Developer/Xcode/DerivedData/TownHall_iPhone-bdlgipvgaapgjhglhromfvcubbxz/Build/Products/Debug-iphonesimulator/TownHall\ iPhone.app/TownHall\ iPhone

Undefined symbols for architecture i386:
  "_main", referenced from:
     implicit entry/start for main executable
     (maybe you meant: _OBJC_IVAR_$_PostTableViewCell._mainTextView, _OBJC_IVAR_$_ConfirmationViewController._mainLabel , _OBJC_IVAR_$_SignInViewController._mainLabel , _OBJC_IVAR_$_SignUpViewController._mainLabel )
ld: symbol(s) not found for architecture i386
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Since this is an error that seems to be able to come from anywhere in the app, I have shared my entire code here: http://ift.tt/1wXtlJO

Any help would be much appreciated.

Thanks!