Adding Bcc support

This adds the `bcc` array to the normalized params.

One important thing to notice here, is that I was having problems running the tests on the master branch. I kept getting an `ArgumentError` from rspec in one of Griddler's testing matchers.

I've submitted a PR there to fix the errors (thoughtbot/griddler#182) but just in case you have the same problem, you can edit the Gemfile to use my fork for now:

```diff
diff --git a/Gemfile b/Gemfile
index 5cb086d..c870f73 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,5 +1,5 @@
 source "https://rubygems.org"
 
-gem "griddler", github: "thoughtbot/griddler"
+gem "griddler", github: "nhocki/griddler", branch: 'fix_rspec_matcher'
 
 gemspec
```

This closes #1 and it's related to thoughtbot/griddler#178.