pass switches to OptionParser.parse opts

[techgaun]

this gets rid of warning on elixir 1.7

warning: not passing the :switches or :strict option to OptionParser is deprecated
  (elixir) lib/option_parser.ex:562: OptionParser.build_config/1
  (elixir) lib/option_parser.ex:197: OptionParser.parse/2
  lib/mix/tasks.ex:18: Mix.Tasks.Coveralls.run/1
  (mix) lib/mix/task.ex:316: Mix.Task.run_task/3
  (mix) lib/mix/cli.ex:79: Mix.CLI.run_task/2

[coveralls]

Coverage increased (+0.2%) to 88.859% when pulling 5ac6315 on techgaun:master into bfa17c9 on parroty:master.

[coveralls]

Coverage increased (+0.2%) to 88.859% when pulling 5ac6315 on techgaun:master into bfa17c9 on parroty:master.

[parroty]

Thanks!