Add .eql() as an alias of .equal()

This is only true when inner elements are all immutable, but #24 shows
up that it should always be the case anyway.

Author: astorije

chai-immutable.js

@@ -83,6 +83,7 @@
      * @name equal
      * @alias equals
      * @alias eq
+     * @alias eql
      * @alias deep.equal
      * @param {Collection} value
      * @api public
@@ -107,6 +108,7 @@
     Assertion.overwriteMethod('equal', assertCollectionEqual);
     Assertion.overwriteMethod('equals', assertCollectionEqual);
     Assertion.overwriteMethod('eq', assertCollectionEqual);
+    Assertion.overwriteMethod('eql', assertCollectionEqual);
 
     /**
      * ### .include(value)

test/test.js

@@ -62,6 +62,8 @@ describe('chai-immutable (' + typeEnv + ')', function () {
         expect(list3).to.not.equals(new List());
         expect(list3).to.eq(List.of(1, 2, 3));
         expect(list3).to.not.eq(new List());
+        expect(list3).to.eql(List.of(1, 2, 3));
+        expect(list3).to.not.eql(new List());
         expect(list3).to.deep.equal(List.of(1, 2, 3));
         expect(list3).to.not.deep.equal(new List());
       });