Minor typographical corrections (#56)

* Minor typographical corrections

* Update spec.md

* your -> those

docs/spec.md

@@ -99,7 +99,7 @@ For example:
  - Two functions are equivalent if they yield equivalent outputs for equivalent inputs.
 
 Note that these examples are not universal, in some cases different
-definitions of equivalense for that types might be more appropriate.
+definitions of equivalence for those types might be more appropriate.
 It depends on which exact abstractions you choose to use in a program.
 
 We use `≡` symbol in laws to denote equivalence.
@@ -108,8 +108,7 @@ We use `≡` symbol in laws to denote equivalence.
 ## Parametricity
 
 All methods' implementations should only use type information about arguments that is known from the signatures.
-It's not allowed to inspect arguments or values that they produce
-or contain to get more information about their types. In other words methods
+Inspecting arguments or values that they produce or contain to get more information about their types is not allowed. In other words methods  
 should be [parametrically polymorphic](https://en.wikipedia.org/wiki/Parametric_polymorphism).