Get search dictionary based on I18n.default_locale (merge pull request #3856)

Implementation tries to be open for further extensions, such as deciding on
search dictionary based on configuration option or by locale set for
given user.

spec/models/debate_spec.rb

@@ -503,7 +503,7 @@ describe Debate do
     end
 
     context "stemming" do
-      it "searches word stems" do
+      it "searches word stems in Spanish", :spanish_search do
         debate = create(:debate, title: "limpiar")
 
         results = Debate.search("limpiará")

spec/models/proposal_spec.rb

@@ -558,7 +558,7 @@ describe Proposal do
     end
 
     context "case" do
-      it "searches case insensite" do
+      it "searches case insensitive" do
         proposal = create(:proposal, title: "SHOUT")
 
         results = Proposal.search("shout")