Do not run specs on jruby-9000 (closes #159)

* See jruby/jruby#3884 for retails
* I'll replace it with add 9.1.1.0 release when it is available

.travis.yml

@@ -10,7 +10,6 @@ rvm:
   - 2.2.5
   - 2.3.1
   - rbx-2
-  - jruby-9000
   - ruby-head
 env:
   global:

spec/integration/schema/predicates/lt_spec.rb

@@ -15,11 +15,10 @@
     end
 
 
-    #https://github.com/dry-rb/dry-validation/issues/159
     context 'with missing input' do
       let(:input) { {} }
 
-      xit 'is not successful' do
+      it 'is not successful' do
         expect(result).to be_failing ['is missing', 'must be less than 23']
       end
     end
@@ -149,8 +148,7 @@
         context 'with missing input' do
           let(:input) { {} }
 
-          #see https://github.com/dry-rb/dry-validation/issues/159
-          xit 'is not successful' do
+          it 'is not successful' do
             expect(result).to be_failing ['is missing', 'must be less than 23']
           end
         end