Change conformance of Array for YAMLRepresentable

Author: aciidgh

Sources/Build/YAML.swift

@@ -26,11 +26,8 @@ extension Bool: YAMLRepresentable {
     }
 }
 
-extension Array: YAMLRepresentable {
+extension Array where Element: YAMLRepresentable {
     var YAML: String {
-        let stringArray = self.flatMap { $0 as? String }
-        guard stringArray.count == self.count else { return "" }
-        
         func quote(input: String) -> String {
             for c in input.characters {
                 if c == "@" || c == " " || c == "-" {
@@ -39,6 +36,7 @@ extension Array: YAMLRepresentable {
             }
             return input
         }
+        let stringArray = self.flatMap { String($0) }
         return "[" + stringArray.map(quote).joinWithSeparator(", ") + "]"
     }
 }