FIX: Make notify work with proper ruby keyword arguments

Fixes #426

lib/honeybadger/agent.rb

@@ -118,20 +118,21 @@ def initialize(opts = {})
     #
     # @return [String] UUID reference to the notice within Honeybadger.
     # @return [false] when ignored.
-    def notify(exception_or_opts, opts = {})
+    def notify(exception_or_opts=nil, opts={}, **kwargs)
       opts = opts.dup
 
       if exception_or_opts.is_a?(Exception)
         already_reported_notice_id = exception_or_opts.instance_variable_get(:@__hb_notice_id)
         return already_reported_notice_id if already_reported_notice_id
-
         opts[:exception] = exception_or_opts
       elsif exception_or_opts.respond_to?(:to_hash)
         opts.merge!(exception_or_opts.to_hash)
-      else
+      elsif !exception_or_opts.nil?
         opts[:error_message] = exception_or_opts.to_s
       end
 
+      opts = opts.merge(kwargs)
+
       validate_notify_opts!(opts)
 
       add_breadcrumb(

lib/honeybadger/singleton.rb

@@ -51,10 +51,10 @@ module Honeybadger
   # @!method notify(...)
   # Forwards to {Agent.instance}.
   # @see Agent#notify
-  def notify(exception_or_opts, opts = {})
+  def notify(exception_or_opts=nil, opts = {}, **kwargs)
     # Note this is defined directly (instead of via forwardable) so that
     # generated stack traces work as expected.
-    Agent.instance.notify(exception_or_opts, opts)
+    Agent.instance.notify(exception_or_opts, opts, **kwargs)
   end
 
   # @api private

spec/unit/honeybadger/agent_spec.rb

@@ -102,7 +102,7 @@
       opts = {error_message: 'test'}
       prev = opts.dup
       instance = described_class.new(Honeybadger::Config.new(api_key: "fake api key", logger: NULL_LOGGER))
-      instance.notify("test", opts)
+      instance.notify("test", **opts)
       expect(prev).to eq(opts)
     end