Remove deprecated execution strategies

.travis.yml

@@ -4,4 +4,5 @@ rvm:
   - 2.2
   - 2.3
   - 2.4
-before_install: gem install bundler -v 1.13.3
+  - 2.5
+  - 2.6

graphql-batch.gemspec

@@ -18,13 +18,12 @@ Gem::Specification.new do |spec|
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ["lib"]
 
-  spec.add_runtime_dependency "graphql", ">= 0.8", "< 2"
+  spec.add_runtime_dependency "graphql", ">= 1.3", "< 2"
   spec.add_runtime_dependency "promise.rb", "~> 0.7.2"
 
   if RUBY_ENGINE == 'ruby' && Gem::Version.new(RUBY_VERSION) >= Gem::Version.new("2.2")
     spec.add_development_dependency "byebug"
   end
-  spec.add_development_dependency "bundler", "~> 1.10"
   spec.add_development_dependency "rake", "~> 10.0"
   spec.add_development_dependency "minitest"
 end

lib/graphql/batch.rb

@@ -1,7 +1,4 @@
 require "graphql"
-if Gem::Version.new(GraphQL::VERSION) < Gem::Version.new("1.3")
-  warn "graphql gem versions less than 1.3 are deprecated for use with graphql-batch, upgrade so lazy_resolve can be used"
-end
 require "promise.rb"
 
 module GraphQL
@@ -31,9 +28,6 @@ def self.use(schema_defn, executor_class: GraphQL::Batch::Executor)
       end
       schema_defn.lazy_resolve(::Promise, :sync)
     end
-
-    autoload :ExecutionStrategy, 'graphql/batch/execution_strategy'
-    autoload :MutationExecutionStrategy, 'graphql/batch/mutation_execution_strategy'
   end
 end