Enable Faraday logger configuration

[agrberg]

Enable passing of logger configuration hash to Faraday for finer logger control.

[closes #86]

[dblock]

This is good, i merged it.

I was wondering whether it would be valuable to write something like this:

IEX::Api::Client.configure do |config|
  config.logger.instance = Logger.new(STDOUT)
  config.logger.options = { bodies: true }
  config.logger.proc = proc { ... }
end

or

IEX::Api::Client.configure do |config|
  config.logger do |logger|
    logger.instance = Logger.new(STDOUT)
    logger.options = { bodies: true }
    logger.proc = proc { ... }
  end
end

If you're bored make a LoggerConfig class that behaves like Config, and it should allow this kind of behavior, avoiding having to do the whole is_a?(Hash) in the implementation, too.

[agrberg]

Popped that in #88. Let me know what you think 👍