Switch from fail to raise

There has been a change to the Ruby Style Guide. See here for recent
discussion: rubocop/rubocop#2732

grape-apiary.gemspec

@@ -32,7 +32,7 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'rspec', '~> 2.14'
   spec.add_development_dependency 'bundler', '~> 1.5'
   spec.add_development_dependency 'rake', '~> 10.0'
-  spec.add_development_dependency 'rubocop', '~> 0.36'
+  spec.add_development_dependency 'rubocop', '>= 0.37', '< 1.0'
   spec.add_development_dependency 'pry', '~> 0.9'
   spec.add_development_dependency 'guard', '~> 2.4'
   spec.add_development_dependency 'guard-rspec', '~> 4.2'

lib/grape-apiary/blueprint.rb

@@ -15,7 +15,7 @@ def generate
     end
 
     def write
-      fail 'Not yet supported'
+      raise 'Not yet supported'
     end
 
     def routes

lib/grape-apiary/config.rb

@@ -35,10 +35,10 @@ def supported_id_types
       end
 
       def example_id_type=(value)
-        fail UnsupportedIDType unless supported_id_types.include?(value)
+        raise UnsupportedIDType unless supported_id_types.include?(value)
 
         if value.to_sym == :bson && !Object.const_defined?('BSON')
-          fail BSONNotDefinied
+          raise BSONNotDefinied
         end
 
         @example_id_type = value

lib/grape-apiary/tasks/grape-apiary.rake

@@ -2,7 +2,7 @@ namespace :ga do
   desc 'Produce documentation'
   task docs: :environment do
     api = ENV['API'] || ARGV[1]
-    fail 'You must provide the name of an API to document' if api.nil?
+    raise 'You must provide the name of an API to document' if api.nil?
     begin
       api_class = Object.const_get(api)
       api_docs = GrapeApiary::Blueprint.new(api_class).generate