Use "soft" dependency with ActiveAdmin version

Add ActiveAdmin versions to the Travis-matrix:
- 1.1.1
- 1.2.1

Author: workgena

.travis.yml

@@ -2,12 +2,12 @@ script: bundle exec rspec spec
 cache: bundler
 env:
   matrix:
-    - RAILS=4.2.6
-    - RAILS=5.0.0
+    - RAILS=4.2.6 AA=1.1.0
+    - RAILS=5.0.0 AA=1.2.1
 rvm:
   - 2.2.6
   - 2.3.3
 before_install:
   - gem update --system
   - rvm @global do gem install bundler -v 1.14.6
-  - gem --version
+  - gem --version

Gemfile

@@ -4,10 +4,11 @@ source 'https://rubygems.org'
 gemspec
 group :test do
   default_rails_version = '4.2.7'
+  default_activeadmin_version = '1.1.0'
   gem 'sprockets-rails', '2.3.3'
   gem 'rails', "#{ENV['RAILS'] || default_rails_version}"
   gem 'rspec-rails'
-  gem 'activeadmin', '1.2.1'
+  gem 'activeadmin', "#{ENV['AA'] || default_activeadmin_version}"
   gem 'coveralls', require: false # Test coverage website. Go to https://coveralls.io
   gem 'sass-rails'
   gem 'sqlite3'

active_admin_datetimepicker.gemspec

@@ -20,7 +20,7 @@ Gem::Specification.new do |spec|
   spec.require_paths = ["lib"]
 
   spec.add_dependency "xdan-datetimepicker-rails", "~> 2.5.1"
-  spec.add_dependency "activeadmin", "~> 1.2.1"
+  spec.add_dependency "activeadmin", "~> 1.1"
   spec.add_development_dependency "bundler", "~> 1.8"
   spec.add_development_dependency "rake", "~> 10.0"