v3.0.0a3

Breaking changes:

• gql-cli script
  • Now printing result as json
  • Now working with multi-lines queries, using Ctrl-D (EOF) to execute queries
  • Using --variables instead of --params

New features:

• File upload support (#145)
• improved gql-cli script (#148)

Bugs corrected:

• DSL allow to use GraphQL keys named type (#151)
• Yarl dependency restricted to <1.6