Rewrite valid? and fix specs

lib/valid_email2/address.rb

@@ -24,25 +24,24 @@ def initialize(address)
     end
 
     def valid?
-      @valid ||= begin
-        return false if @parse_error
+      return @valid if @valid != nil
+      return false  if @parse_error
 
+      @valid = begin
         if address.domain && address.address == @raw_address
           domain = address.domain
 
           domain !~ PROHIBITED_DOMAIN_CHARACTERS_REGEX &&
             # Domain needs to have at least one dot
-            domain =~ /\./ &&
+            domain.include?('.') &&
             # Domain may not have two consecutive dots
-            domain !~ /\.{2,}/ &&
+            !domain.include?('..') &&
             # Domain may not start with a dot
-            domain !~ /^\./ &&
+            !domain.start_with?('.') &&
             # Domain may not start with a dash
-            domain !~ /^-/ &&
+            !domain.start_with?('-') &&
             # Domain name may not end with a dash
-            domain !~ /-\./ &&
-            # Address may not contain a dot directly before @
-            address.address !~ /\.@/
+            !domain.include?('-.')
         else
           false
         end

spec/valid_email2_spec.rb

@@ -82,16 +82,11 @@ class TestUserMessage < TestModel
       expect(user.valid?).to be_falsey
     end
 
-    it "is invalid if the domain contains emoticons" do
+    it "is invalid if the email contains emoticons" do
       user = TestUser.new(email: "foo🙈@gmail.com")
       expect(user.valid?).to be_falsy
     end
 
-    it "is invalid if the domain contains .@ consecutively" do
-      user = TestUser.new(email: "foo.@gmail.com")
-      expect(user.valid?).to be_falsy
-    end
-
     it "is invalid if the domain contains spaces" do
       user = TestUser.new(email: "user@gmail .com")
       expect(user.valid?).to be_falsy