excon is a dependency

[edsu]

At the moment excon is listed as s development dependency but it's needed outside of development as well:

zen:~ ed$ gem install wikidata-client
Fetching: multipart-post-2.0.0.gem (100%)
Successfully installed multipart-post-2.0.0
Fetching: faraday-0.9.1.gem (100%)
Successfully installed faraday-0.9.1
Fetching: faraday_middleware-0.9.1.gem (100%)
Successfully installed faraday_middleware-0.9.1
Fetching: wikidata-client-0.0.6.gem (100%)
Successfully installed wikidata-client-0.0.6
invalid options: -SHN
(invalid options are ignored)
Parsing documentation for multipart-post-2.0.0
Installing ri documentation for multipart-post-2.0.0
Parsing documentation for faraday-0.9.1
Installing ri documentation for faraday-0.9.1
Parsing documentation for faraday_middleware-0.9.1
Installing ri documentation for faraday_middleware-0.9.1
Parsing documentation for wikidata-client-0.0.6
Installing ri documentation for wikidata-client-0.0.6
Done installing documentation for multipart-post, faraday, faraday_middleware, wikidata-client after 1 seconds
4 gems installed
zen:~ ed$ irb
2.2.1 :001 > require 'wikidata'
 => true
2.2.1 :002 > Wikidata::Item.find('Q6882')
RuntimeError: missing dependency for Faraday::Adapter::Excon: cannot load such file -- excon
    from /Users/ed/.rvm/gems/ruby-2.2.1@test/gems/faraday-0.9.1/lib/faraday/middleware.rb:20:in `new'
    from /Users/ed/.rvm/gems/ruby-2.2.1@test/gems/faraday-0.9.1/lib/faraday/rack_builder.rb:48:in `build'
    from /Users/ed/.rvm/gems/ruby-2.2.1@test/gems/faraday-0.9.1/lib/faraday/rack_builder.rb:162:in `block in to_app'
    from /Users/ed/.rvm/gems/ruby-2.2.1@test/gems/faraday-0.9.1/lib/faraday/rack_builder.rb:162:in `each'
    from /Users/ed/.rvm/gems/ruby-2.2.1@test/gems/faraday-0.9.1/lib/faraday/rack_builder.rb:162:in `inject'
    from /Users/ed/.rvm/gems/ruby-2.2.1@test/gems/faraday-0.9.1/lib/faraday/rack_builder.rb:162:in `to_app'
    from /Users/ed/.rvm/gems/ruby-2.2.1@test/gems/faraday-0.9.1/lib/faraday/rack_builder.rb:152:in `app'
    from /Users/ed/.rvm/gems/ruby-2.2.1@test/gems/faraday-0.9.1/lib/faraday/rack_builder.rb:139:in `build_response'
    from /Users/ed/.rvm/gems/ruby-2.2.1@test/gems/faraday-0.9.1/lib/faraday/connection.rb:377:in `run_request'
    from /Users/ed/.rvm/gems/ruby-2.2.1@test/gems/faraday-0.9.1/lib/faraday/connection.rb:140:in `get'
    from /Users/ed/.rvm/gems/ruby-2.2.1@test/gems/wikidata-client-0.0.6/lib/wikidata/client.rb:14:in `response'
    from /Users/ed/.rvm/gems/ruby-2.2.1@test/gems/wikidata-client-0.0.6/lib/wikidata/item.rb:29:in `_find'
    from /Users/ed/.rvm/gems/ruby-2.2.1@test/gems/wikidata-client-0.0.6/lib/wikidata/item.rb:18:in `find'
    from (irb):2
    from /Users/ed/.rvm/rubies/ruby-2.2.1/bin/irb:11:in `<main>'