add gemspec

Gemfile

@@ -1,3 +1,4 @@
 source 'https://rubygems.org'
 
 gem 'github-pages'
+gemspec

cayman.gemspec

@@ -0,0 +1,17 @@
+# encoding: utf-8
+
+Gem::Specification.new do |s|
+  s.name          = "jekyll-cayman"
+  s.version       = "0.0.1"
+  s.authors       = ["Jason Long"]
+  s.email         = ["[email protected]"]
+  s.homepage      = "https://github.com/pages-themes/cayman"
+  s.summary       = "Cayman is a clean, responsive theme for GitHub Pages"
+
+  s.files         = `git ls-files -z`.split("\x0").select do |f|
+    f.match(%r{^(_(includes|layouts|sass)/|(LICENSE|README)((\.(txt|md|markdown)|$)))}i)
+  end
+
+  s.platform      = Gem::Platform::RUBY
+  s.add_runtime_dependency "jekyll", "~> 3.2"
+end