Make compatible with 3.2.x and 4.x and add travis CI tests for both

.travis.yml

@@ -3,3 +3,6 @@ rvm:
   - 2.0.0
   - 1.9.3
   - rbx-19mode
+env:
+  - "RAILS_VERSION=~> 3.2"
+  - "RAILS_VERSION=~> 4.0"

Gemfile

@@ -1,2 +1,7 @@
 source "https://rubygems.org"
 gemspec
+
+if ENV['RAILS_VERSION']
+  gem 'rails', ENV['RAILS_VERSION']
+end
+

lib/migrant/migration_generator.rb

@@ -8,7 +8,9 @@ def run
       FileUtils.mkdir_p(Rails.root.join('db', 'migrate'))
       @possible_irreversible_migrations = false
 
-      migrator = ActiveRecord::Migrator.open(migrations_path)
+      migrator = (ActiveRecord::Migrator.public_methods.include?(:open))? 
+                  ActiveRecord::Migrator.open(migrations_path) : 
+                  ActiveRecord::Migrator.new(:up, migrations_path)
 
       unless migrator.pending_migrations.blank?
         log "You have some pending database migrations. You can either:\n1. Run them with rake db:migrate\n2. Delete them, in which case this task will probably recreate their actions (DON'T do this if they've been in SCM).", :error