Improve boolean string mapping

Consider "true" and "1" to be equal to true and "false", "0" to be
false when mapping booleans.

Otherwise return nil.

Sources/Shared/Extensions/Dictionary+Tailor.swift

@@ -101,7 +101,14 @@ public extension Dictionary {
     }
 
     if let string = self[key] as? String {
-      return string == "true" ? true : false
+
+      if ["true", "1"].contains(string.lowercased()) {
+        return true
+      } else if ["false", "0"].contains(string.lowercased()) {
+        return false
+      }
+
+      return nil
     } else if let number = self[key] as? NSNumber {
       return number.boolValue
     } else if let boolean = self[key] as? Bool {

TailorTests/Shared/DefaultTypesMappingTests.swift

@@ -14,6 +14,7 @@ class TestMappingDefaultTypes: QuickSpec {
         "float": 2.5,
         "bool" : true,
         "string_bool" : "true",
+        "string_number_bool" : "1",
         "string": "1.25",
         "array" : [
           "foo", "bar", "baz"
@@ -44,6 +45,7 @@ class TestMappingDefaultTypes: QuickSpec {
 
         expect(dictionary.value(forKey: "bool", ofType: Bool.self)).to(equal(true))
         expect(dictionary.value(forKey: "string_bool", ofType: Bool.self)).to(equal(true))
+        expect(dictionary.value(forKey: "string_number_bool", ofType: Bool.self)).to(equal(true))
 
         expect(dictionary.string("string")).to(equal("1.25"))
 
@@ -67,6 +69,8 @@ class TestMappingDefaultTypes: QuickSpec {
         expect(dictionary.int("string")).to(equal(1))
         expect(dictionary.string("string")).to(equal("1.25"))
 
+        expect(dictionary.boolean("string_number_bool")).to(equal(true))
+
       }
     }
   }