Update copyright year

Demo/Demo/Kingfisher-Demo/Base.lproj/LaunchScreen.xib

@@ -15,7 +15,7 @@
             <rect key="frame" x="0.0" y="0.0" width="480" height="480"/>
             <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
             <subviews>
-                <label opaque="NO" clipsSubviews="YES" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" text="  Copyright (c) 2018年 Wei Wang. All rights reserved." textAlignment="center" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" minimumFontSize="9" translatesAutoresizingMaskIntoConstraints="NO" id="8ie-xW-0ye">
+                <label opaque="NO" clipsSubviews="YES" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" text="  Copyright (c) 2019 Wei Wang (onevcat). All rights reserved." textAlignment="center" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" minimumFontSize="9" translatesAutoresizingMaskIntoConstraints="NO" id="8ie-xW-0ye">
                     <rect key="frame" x="20" y="439" width="441" height="21"/>
                     <fontDescription key="fontDescription" type="system" pointSize="17"/>
                     <color key="textColor" cocoaTouchSystemColor="darkTextColor"/>

Tests/KingfisherTests/StringExtensionTests.swift

@@ -3,7 +3,7 @@
 //  Kingfisher
 //
 //  Created by Wei Wang on 16/8/14.
-//  Copyright © 2018年 Wei Wang. All rights reserved.
+//  Copyright © 2019 Wei Wang. All rights reserved.
 //
 
 import XCTest