Add hashie gem to dependencies

[dogwood008]

Add hashie gem to dependencies. It is required not to fail at here. If not, I got this when I run bundle exec rails c :

$ bundle exec rails c
/Users/user/path/to/project/vendor/bundle/ruby/2.4.0/bundler/gems/grape-jbuilder-b6e8d3daef7f/lib/grape/jbuilder.rb:2:in `require': cannot load such file -- hashie/hash (LoadError)
	from /Users/user/path/to/project/vendor/bundle/ruby/2.4.0/bundler/gems/grape-jbuilder-b6e8d3daef7f/lib/grape/jbuilder.rb:2:in `<top (required)>'
	from /usr/local/lib/ruby/gems/2.4.0/gems/bundler-1.14.4/lib/bundler/runtime.rb:105:in `require'
	from /usr/local/lib/ruby/gems/2.4.0/gems/bundler-1.14.4/lib/bundler/runtime.rb:105:in `rescue in block in require'
	from /usr/local/lib/ruby/gems/2.4.0/gems/bundler-1.14.4/lib/bundler/runtime.rb:82:in `block in require'
	from /usr/local/lib/ruby/gems/2.4.0/gems/bundler-1.14.4/lib/bundler/runtime.rb:75:in `each'
	from /usr/local/lib/ruby/gems/2.4.0/gems/bundler-1.14.4/lib/bundler/runtime.rb:75:in `require'
	from /usr/local/lib/ruby/gems/2.4.0/gems/bundler-1.14.4/lib/bundler.rb:107:in `require'
	from /Users/user/path/to/project/config/application.rb:7:in `<top (required)>'
	from /Users/user/path/to/project/vendor/bundle/ruby/2.4.0/gems/railties-5.1.2/lib/rails/command/actions.rb:15:in `require'
	from /Users/user/path/to/project/vendor/bundle/ruby/2.4.0/gems/railties-5.1.2/lib/rails/command/actions.rb:15:in `require_application_and_environment!'
	from /Users/user/path/to/project/vendor/bundle/ruby/2.4.0/gems/railties-5.1.2/lib/rails/commands/console/console_command.rb:84:in `perform'
	from /Users/user/path/to/project/vendor/bundle/ruby/2.4.0/gems/thor-0.19.4/lib/thor/command.rb:27:in `run'
	from /Users/user/path/to/project/vendor/bundle/ruby/2.4.0/gems/thor-0.19.4/lib/thor/invocation.rb:126:in `invoke_command'
	from /Users/user/path/to/project/vendor/bundle/ruby/2.4.0/gems/thor-0.19.4/lib/thor.rb:369:in `dispatch'
	from /Users/user/path/to/project/vendor/bundle/ruby/2.4.0/gems/railties-5.1.2/lib/rails/command/base.rb:63:in `perform'
	from /Users/user/path/to/project/vendor/bundle/ruby/2.4.0/gems/railties-5.1.2/lib/rails/command.rb:44:in `invoke'
	from /Users/user/path/to/project/vendor/bundle/ruby/2.4.0/gems/railties-5.1.2/lib/rails/commands.rb:16:in `<top (required)>'
	from bin/rails:4:in `require'
	from bin/rails:4:in `<main>'

$ sw_vers
ProductName:	Mac OS X
ProductVersion:	10.12.4
BuildVersion:	16E195