Re-implemented all development Rake tasks in Thor. Now actually tested.

Fixes:
* https://www.pivotaltracker.com/story/show/25484287 & https://github.com/pivotal/jasmine/issues/183
* https://www.pivotaltracker.com/story/show/25485401 & https://github.com/pivotal/jasmine/issues/189
* https://www.pivotaltracker.com/story/show/25485953 & https://github.com/pivotal/jasmine/issues/159

tasks/jasmine_dev/build_github_pages.rb

@@ -0,0 +1,18 @@
+class JasmineDev < Thor
+
+  desc "build_github_pages", "Build static pages for pivotal.github.com/jasmine"
+  def build_github_pages(pages_dir = File.expand_path(File.join('.', 'pages')))
+    say JasmineDev.spacer
+
+    say "Building Github Pages...", :cyan
+
+    return unless pages_submodule_installed?
+
+    pages_output = File.join(pages_dir, 'pages_output')
+    FileUtils.rm_r(pages_output) if File.exist?(pages_output)
+
+    inside File.join('pages', 'pages_source') do
+      run_with_output "frank export #{pages_output}", :capture => true
+    end
+  end
+end