fix: add comment about rbacwithadmin being rather powerful (#936)

* fix: add comment about rbacwithadmin being rather powerful
* fix: move RBACWithAdmin to examples

contracts/examples/RBACWithAdmin.sol

@@ -0,0 +1,67 @@
+pragma solidity ^0.4.23;
+
+import "../ownership/rbac/RBAC.sol";
+
+
+/**
+ * @title RBACWithAdmin
+ * @author Matt Condon (@Shrugs)
+ * @dev It's recommended that you define constants in the contract,
+ * @dev like ROLE_ADMIN below, to avoid typos.
+ * @dev
+ * @dev NOTE: RBACWithAdmin is probably too expansive and powerful for your
+ * @dev  application; an admin is actually able to change any address to any role
+ * @dev  which is a very large API surface. It's recommended that you follow a strategy
+ * @dev  of strictly defining the abilities of your roles
+ * @dev  and the API-surface of your contract.
+ * @dev  This is just an example for example's sake.
+ */
+contract RBACWithAdmin is RBAC {
+  /**
+   * A constant role name for indicating admins.
+   */
+  string public constant ROLE_ADMIN = "admin";
+
+  /**
+   * @dev modifier to scope access to admins
+   * // reverts
+   */
+  modifier onlyAdmin()
+  {
+    checkRole(msg.sender, ROLE_ADMIN);
+    _;
+  }
+
+  /**
+   * @dev constructor. Sets msg.sender as admin by default
+   */
+  constructor()
+    public
+  {
+    addRole(msg.sender, ROLE_ADMIN);
+  }
+
+  /**
+   * @dev add a role to an address
+   * @param addr address
+   * @param roleName the name of the role
+   */
+  function adminAddRole(address addr, string roleName)
+    onlyAdmin
+    public
+  {
+    addRole(addr, roleName);
+  }
+
+  /**
+   * @dev remove a role from an address
+   * @param addr address
+   * @param roleName the name of the role
+   */
+  function adminRemoveRole(address addr, string roleName)
+    onlyAdmin
+    public
+  {
+    removeRole(addr, roleName);
+  }
+}