Change gemspec to add metadata and remove file artifacts

tty-tree.gemspec

@@ -1,25 +1,30 @@
-lib = File.expand_path('../lib', __FILE__)
+lib = File.expand_path("../lib", __FILE__)
 $LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
-require 'tty/tree/version'
+require "tty/tree/version"
 
 Gem::Specification.new do |spec|
   spec.name          = "tty-tree"
   spec.version       = TTY::Tree::VERSION
   spec.authors       = ["Piotr Murach"]
   spec.email         = ["me@piotrmurach.com"]
-
   spec.summary       = %q{Print directory or structured data in a tree like format.}
   spec.description   = %q{Print directory or structured data in a tree like format.}
   spec.homepage      = "https://piotrmurach.github.io/tty"
   spec.license       = "MIT"
-
-  spec.files         = Dir['{lib,spec}/**/*.rb', '{bin,tasks}/*', 'tty-tree.gemspec']
-  spec.files        += Dir['README.md', 'CHANGELOG.md', 'LICENSE.txt', 'Rakefile']
-  spec.bindir        = "exe"
-  spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
+  if spec.respond_to?(:metadata=)
+    spec.metadata = {
+      "allowed_push_host" => "https://rubygems.org",
+      "bug_tracker_uri"   => "https://github.com/piotrmurach/tty-tree/issues",
+      "changelog_uri"     => "https://github.com/piotrmurach/tty-tree/blob/master/CHANGELOG.md",
+      "documentation_uri" => "https://www.rubydoc.info/gems/tty-tree",
+      "homepage_uri"      => spec.homepage,
+      "source_code_uri"   => "https://github.com/piotrmurach/tty-tree"
+    }
+  end
+  spec.files         = Dir["lib/**/*", "README.md", "CHANGELOG.md", "LICENSE.txt"]
+  spec.executables   = []
   spec.require_paths = ["lib"]
-
-  spec.required_ruby_version = '>= 2.0.0'
+  spec.required_ruby_version = ">= 2.0.0"
 
   spec.add_development_dependency "bundler", ">= 1.14.0"
   spec.add_development_dependency "rake"