Frescobaldi updated to version 2.18

Closes Homebrew/homebrew#39107.

Signed-off-by: Dominyk Tiller <dominyktiller@gmail.com>

Formula/frescobaldi.rb

@@ -2,15 +2,15 @@ require "formula"
 
 class Frescobaldi < Formula
   homepage "http://frescobaldi.org/"
-  url "https://github.com/wbsoft/frescobaldi/releases/download/v2.0.16/frescobaldi-2.0.16.tar.gz"
-  sha1 "6b7e72def3f93aa9521d7a1cdb72399f1a5765c5"
+  url "https://github.com/wbsoft/frescobaldi/releases/download/v2.18/frescobaldi-2.18.tar.gz"
+  sha256 "6531a6425a0b0a471fb0845098e9c890e59d6379636ed79b4512a48599327d4b"
 
   option "without-launcher", "Don't build Mac .app launcher"
   option "without-lilypond", "Don't install Lilypond"
 
   depends_on :python if MacOS.version <= :snow_leopard
-  depends_on "portmidi" => :recommended
-  depends_on "lilypond" => :recommended
+  depends_on "portmidi" => :optional
+  depends_on "lilypond" => :optional
 
   # python-poppler-qt4 dependencies
   depends_on "poppler" => "with-qt"
@@ -22,11 +22,19 @@ class Frescobaldi < Formula
     sha1 "584345ae2fae2e1d667222cafa404a241cf95a1f"
   end
 
+  resource "python-ly" do
+    url "https://pypi.python.org/packages/source/p/python-ly/python-ly-0.9.1.tar.gz"
+    sha1 "0c9eaab04484c99eeab645a66c19ab499afb2c1d"
+  end
+
   def install
     ENV.prepend_create_path "PYTHONPATH", libexec/"vendor/lib/python2.7/site-packages"
     resource("python-poppler-qt4").stage do
       system "python", *Language::Python.setup_install_args(libexec/"vendor")
     end
+    resource("python-ly").stage do
+      system "python", *Language::Python.setup_install_args(libexec/"vendor")
+    end
 
     ENV.prepend_create_path "PYTHONPATH", libexec/"lib/python2.7/site-packages"
     rm "setup.cfg"
@@ -47,4 +55,16 @@ class Frescobaldi < Formula
   test do
     system bin/"frescobaldi", "--version"
   end
+
+  def caveats
+    s = <<-EOS.undent
+      By default, a splash screen is shown on startup; this causes the main
+      window not to show until the application icon on the dock is clicked
+      (Cmd-Tab application switching does not appear to work). You may
+      want to disable the splash screen in the preferences to solve this
+      issue. See:
+        https://github.com/wbsoft/frescobaldi/issues/428
+    EOS
+    return s
+  end
 end