Fix SimpleCov MultiFormatter deprecation
Fix SimpleCov MultiFormatter deprecation

Here's an example of the error message:
https://travis-ci.org/Homebrew/homebrew-bundle/builds/163380130#L278

Here's where an alternative new syntax is documented:
https://github.com/colszowka/simplecov/tree/e0accd692594645c836f2a771692b19c21397e41#using-multiple-formatters

Here's an example of the new syntax being used in SimpleCov itself:
https://github.com/colszowka/simplecov/commit/ddde04d4c9e2359ae7dcfdf27a247c61b238cb07#diff-6fc312203870a48a45997f6c5602040eL131

Homebrew/homebrew-bundle