C4.S01 - As a Developer, I should be able to search for keywords in English and Arabic

@adamggg @m0hamed @nourhanZ @mostafahassaan please review
Issue #74 is concerned ;)

Files Changed:
Views: search_keywords.html.erb
Controllers: search_keyword.rb
Models: keyword.rb (method: get_similar_keywords)
Tests: spec/models/keyword_spec.rb (lines 81-163) 
UML: C4.S01.png