Fix missing environment dependency for import tasks

Author: eliias

Diff for: elasticsearch-rails/lib/elasticsearch/rails/tasks/import.rb

@@ -57,7 +57,7 @@
         $ rake environment elasticsearch:import:model CLASS='Article' SCOPE='published'
     DESC
     desc import_model_desc
-    task :model do
+    task model: :environment do
       if ENV['CLASS'].to_s == ''
         puts '='*90, 'USAGE', '='*90, import_model_desc, ""
         exit(1)
@@ -97,7 +97,7 @@
 
         $ rake environment elasticsearch:import:all DIR=app/models
     DESC
-    task :all do
+    task all: :environment do
       dir    = ENV['DIR'].to_s != '' ? ENV['DIR'] : Rails.root.join("app/models")
 
       puts "[IMPORT] Loading models from: #{dir}"