Modifying Version init to preserve old init

There are dependencies on the init being available with only the string argument

Author: colincornaby

Sources/TSCUtility/Version.swift

@@ -104,13 +104,21 @@ extension Version: CustomStringConvertible {
 }
 
 public extension Version {
+    
+    /// Create a version object from string.
+    ///
+    /// - Parameters:
+    ///   - string: The string to parse.
+    init?(string: String) {
+        self.init(string: string, lenient: false)
+    }
 
     /// Create a version object from string.
     ///
     /// - Parameters:
     ///   - string: The string to parse.
     ///   - lenient: Boolean indicating if partial strings should be parsed. Infers that strings without an explicit patch version have a patch version of zero. Defaults to false.   
-    init?(string: String, lenient: Bool = false) {
+    init?(string: String, lenient: Bool) {
         let prereleaseStartIndex = string.firstIndex(of: "-")
         let metadataStartIndex = string.firstIndex(of: "+")