Delete local Homebrew Formula now that it's in homebrew-core

See #32

HomebrewFormula/mkcert.rb

@@ -1,18 +0,0 @@
-class Mkcert < Formula
-  desc "Simple tool to make locally-trusted development certificates"
-  homepage "https://github.com/FiloSottile/mkcert"
-  head "https://github.com/FiloSottile/mkcert.git"
-
-  depends_on "go" => :build
-
-  def install
-    ENV["GOPATH"] = buildpath
-    mkcertpath = buildpath/"src/github.com/FiloSottile/mkcert"
-    mkcertpath.install buildpath.children
-    cd mkcertpath do
-      system "go", "build", "-o", bin/"mkcert"
-      prefix.install_metafiles
-    end
-  end
-end
-