Bump required Ruby version and update travis.yml

Rails 5 requires Ruby 2.2.2 and will fail on versions lower than 2.2.1.
This change removes the versions that cannot work with the changes to
Rails 5 and actionpack-xml_parser. Updates corresponding .travis.yml
file so that master no longer runs against those.

.travis.yml

@@ -1,8 +1,6 @@
 language: ruby
 sudo: false
 rvm:
-  - 1.9
-  - 2.0
   - 2.1
   - 2.2
   - ruby-head
@@ -18,9 +16,5 @@ matrix:
   allow_failures:
     - rvm: ruby-head
   exclude:
-    - rvm: 1.9
-      gemfile: gemfiles/Gemfile-edge
-    - rvm: 2.0
-      gemfile: gemfiles/Gemfile-edge
     - rvm: 2.1
       gemfile: gemfiles/Gemfile-edge

actionpack-xml_parser.gemspec

@@ -1,10 +1,10 @@
 Gem::Specification.new do |s|
   s.platform    = Gem::Platform::RUBY
   s.name        = 'actionpack-xml_parser'
-  s.version     = '1.0.2'
+  s.version     = '2.0.0'
   s.summary     = 'XML parameters parser for Action Pack (removed from core in Rails 4.0)'
 
-  s.required_ruby_version = '>= 1.9.3'
+  s.required_ruby_version = '>= 2.2.1'
   s.license     = 'MIT'
 
   s.author      = 'Prem Sichanugrist'