Upgrading drivers breaks Feria on MacOS X 10.12.4

[SiAdcock]

I'm currently seeing the following issue when running Feria on my machine:

Exception in thread "main" org.openqa.selenium.SessionNotCreatedException: Unable to create new remote session. desired capabilities = Capabilities [{marionette=true, firefoxOptions=org.openqa.selenium.firefox.FirefoxOptions@38c6f217, browserName=firefox, moz:firefoxOptions=org.openqa.selenium.firefox.FirefoxOptions@38c6f217, version=, platform=ANY, firefox_profile=org.openqa.selenium.firefox.F...}], required capabilities = Capabilities [{}]
Build info: version: 'unknown', revision: 'unknown', time: 'unknown'
System info: host: '34643', ip: '0.0.135.83', os.name: 'Mac OS X', os.arch: 'x86_64', os.version: '10.12.4', java.version: '1.8.0_91'
Driver info: driver.version: FirefoxDriver
	at org.openqa.selenium.remote.ProtocolHandshake.createSession(ProtocolHandshake.java:91)
	at org.openqa.selenium.remote.HttpCommandExecutor.execute(HttpCommandExecutor.java:141)
	at org.openqa.selenium.remote.service.DriverCommandExecutor.execute(DriverCommandExecutor.java:82)
	at org.openqa.selenium.remote.RemoteWebDriver.execute(RemoteWebDriver.java:601)
	at org.openqa.selenium.remote.RemoteWebDriver.startSession(RemoteWebDriver.java:241)
	at org.openqa.selenium.remote.RemoteWebDriver.<init>(RemoteWebDriver.java:128)
	at org.openqa.selenium.firefox.FirefoxDriver.<init>(FirefoxDriver.java:259)
	at org.openqa.selenium.firefox.FirefoxDriver.<init>(FirefoxDriver.java:247)
	at org.openqa.selenium.firefox.FirefoxDriver.<init>(FirefoxDriver.java:242)
	at org.openqa.selenium.firefox.FirefoxDriver.<init>(FirefoxDriver.java:135)
	at feria.Feria$$anonfun$5.apply(Feria.scala:52)
	at feria.Feria$$anonfun$5.apply(Feria.scala:44)
	at scala.Option.map(Option.scala:146)
	at feria.Feria$.run(Feria.scala:44)
	at feria.Feria$$anonfun$4.apply(Feria.scala:41)
	at feria.Feria$$anonfun$4.apply(Feria.scala:41)
	at scala.Option.map(Option.scala:146)
	at feria.Feria$.delayedEndpoint$feria$Feria$1(Feria.scala:41)
	at feria.Feria$delayedInit$body.apply(Feria.scala:15)
	at scala.Function0$class.apply$mcV$sp(Function0.scala:34)
	at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:12)
	at scala.App$$anonfun$main$1.apply(App.scala:76)
	at scala.App$$anonfun$main$1.apply(App.scala:76)
	at scala.collection.immutable.List.foreach(List.scala:381)
	at scala.collection.generic.TraversableForwarder$class.foreach(TraversableForwarder.scala:35)
	at scala.App$class.main(App.scala:76)
	at feria.Feria$.main(Feria.scala:15)
	at feria.Feria.main(Feria.scala)

I am able to use Feria if I hard reset back to d533abc. This leads me to believe the issue was introduced in #17. I'm running Firefox v55.0.3.

Please let me know if you need any further info.