Elixir 1.8.1 warnings could be removed

[gorenje]

I get some warnings using 1.8.1:

warning: invalid type annotation. When using the | operator to represent the union of types, make sure to wrap type annotations in parentheses: nil | number | opts :: Keyword.t()
  lib/kafka_ex/server.ex:232

and

warning: System.cwd/0 is deprecated. Use File.cwd/0 instead
  config/config.exs:60

warning: System.cwd/0 is deprecated. Use File.cwd/0 instead
  config/config.exs:61

warning: System.cwd/0 is deprecated. Use File.cwd/0 instead
  config/config.exs:62

this would remove them but dunno what it does on other Elixir versions.

[joshuawscott]

👍 Thanks for cleaning this up!

[bjhaid]

can you add 1.8.1 to the mix here:

kafka_ex/.travis.yml

Lines 10 to 25 in 3c1eaf8

	include:
	- elixir: 1.7.4
	otp_release: 21.1
	- elixir: 1.6.6
	otp_release: 20.2
	- elixir: 1.5.3
	otp_release: 20.2
	- elixir: 1.4.5
	otp_release: 19.3
	env: COVERALLS=true CREDO=true
	- elixir: 1.3.4
	otp_release: 19.3
	- elixir: 1.2.6
	otp_release: 18.3
	- elixir: 1.1.1
	otp_release: 18.3

❤️

[gorenje]

Thank you for a great package :)