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/execute_specs.rb

@@ -0,0 +1,52 @@
+class JasmineDev < Thor
+
+  desc "execute_specs_in_node", "Run all relevant specs in Node.js"
+
+  def execute_specs_in_node
+    return unless node_installed?
+
+    invoke :build_distribution
+    invoke :count_specs
+
+    say JasmineDev.spacer
+
+    say "Running all appropriate specs via Node.js...", :cyan
+
+    with_color_option = Term::ANSIColor.coloring? ? "--color" : "--noColor"
+
+    run_with_output "node spec/node_suite.js #{with_color_option}", :capture => true
+  end
+
+  desc "execute_specs_in_browser", "Run all relevent specs in your default browser"
+
+  def execute_specs_in_browser
+    invoke :build_distribution
+    invoke :count_specs
+
+    say JasmineDev.spacer
+
+    say "Running all appropriate specs via the default web browser...", :cyan
+
+    open_specs_in_browser
+  end
+
+  desc "execute_specs", "Run all of Jasmine's specs"
+
+  def execute_specs
+    invoke :execute_specs_in_node
+    invoke :execute_specs_in_browser
+  end
+
+  no_tasks do
+    def open_specs_in_browser
+      require 'rbconfig'
+
+      case Object.const_get(defined?(RbConfig) ? :RbConfig : :Config)::CONFIG['host_os']
+        when /linux/
+          run "xdg-open spec/runner.html"
+        else
+          run "open spec/runner.html"
+      end
+    end
+  end
+end