Use a remporary file to run groovy scripts

Here documents (using <<-GROOVYSCRIPT) do not work properly on windows,
specifically Powershell. This commit switches to using Ruby's tempfile.
Allow attribute overrides to work properly
Use travis namespace for 'ci' rake task.  Fixes #202.
Merge pull request #203 from opscode-cookbooks/yzl/issue-202

Use travis namespace for 'ci' rake task.  Fixes #202.
Use executor['timeout'] for timeout in ShellOut in executor.execute!
Give timeout a default value (60) in the executor