Fixed typos

README.md

@@ -202,7 +202,7 @@ class Subclass: Base {
 # Mapping Immutable Properties
 If you have a class or struct whose properties are immutable (`let`) and want to map it using ObjectMapper, you can use the following approach.
 
-In the failable initializer, assign values to your proteries using the `valueOrFail()` function on the `map` object. Once all propeties are set, check `isValid` to determine if mapping succeed for all the properties. If `isValid` returns false, return `nil` to indicate that initialization failed.
+In the failable initializer, assign values to your properties using the `valueOrFail()` function on the `map` object. Once all propeties are set, check `isValid` to determine if the mapping succeeded for all properties. If `isValid` returns false, return `nil` to indicate that initialization failed.
 
 ```swift
 class Model: Mappable {