Update to new SHA256() API in the core

.travis.yml

@@ -1,5 +1,5 @@
 language: objective-c
-osx_image: xcode11.2
+osx_image: xcode11.4
 
 env:
   - ACTION=test  PLATFORM=Mac     DESTINATION='platform=OS X'

Sources/SourceParsingFramework/Utilities/Extensions.swift

@@ -22,7 +22,7 @@ extension String {
 
     /// The SHA256 value of this String.
     public var shortSHA256Value: String {
-        return SHA256(self).digestString().substring(with: NSRange(location: 0, length: 20))!
+        return SHA256().hash(self).hexadecimalRepresentation.substring(with: NSRange(location: 0, length: 20))!
     }
 
     /// Return the same String with the first character lowercased.

Tests/SourceParsingFrameworkTests/Utilities/ExtensionsTests.swift

@@ -30,6 +30,12 @@ class ExtensionsTests: AbstractSourceParsingTests {
         dirPath = String(filePath.prefix(upTo: index))
     }
 
+    func test_sha256_verifyResults() {
+        let input = "Some random string"
+        let sha256 = input.shortSHA256Value
+        XCTAssertEqual(sha256, "7e2ab276842ae9fb52ae")
+    }
+
     func test_isDirectory_verifyResults() {
         XCTAssertFalse(filePath.isDirectory)
         XCTAssertTrue(dirPath.isDirectory)