Enable SSL verification for Webhooks

CHANGELOG

app/controllers/admin/hooks_controller.rb

app/controllers/projects/hooks_controller.rb

app/controllers/projects/services_controller.rb

app/models/hooks/web_hook.rb

app/models/project_services/buildkite_service.rb

app/models/project_services/gitlab_ci_service.rb

app/views/admin/hooks/index.html.haml

app/views/projects/hooks/index.html.haml

db/migrate/20150824002011_add_enable_ssl_verification.rb

db/schema.rb

features/admin/hooks.feature

features/project/hooks.feature

features/steps/admin/hooks.rb

features/steps/project/hooks.rb