Fixed claim check in JwtValidator

* Removed the addRequiredClaimWithValue() method, as checking
  the value should be up to the implementation.

README.md

@@ -78,10 +78,8 @@ Parsing is done by passing the raw token as the 2nd parameter
     use NoccyLabs\SimpleJwt\Validator\JwtValidator;
 
     $validator = new JwtValidator();
-    // Require that the claim exists
+    // Require that some claim exists
     $validator->addRequiredClaim("some/required/Claim");
-    // Require that the claim exists and has a value of true
-    $validator->addRequiredClaimWithValue("some/required/OtherClaim", true);
 
     try {
         // Pass a JwtToken to validateToken()...

src/Validator/JwtValidator.php

@@ -21,12 +21,10 @@ class JwtValidator
 
     public function addRequiredClaim(string $name)
     {
-        $this->requireClaims[$name] = true;
-    }
-
-    public function addRequiredClaimWithValue(string $name, $value)
-    {
-        $this->requireClaims[$name] = [ $value ];
+        if (!in_array($name, $this->requireClaims)) {
+            return;
+        }
+        $this->requireClaims[] = $name;
     }
 
     public function validateToken(JwtToken $token)