A start at a gem-based plugin whitelist for Pages.
Add --whitelist flag and internal logic
Remove Site.whitelist attribute.
Add test code for 'whitelist' option.
Remove option from CLI
Add "jekyll_test_plugin_malicious" as gem dep
The whitelist should be an array (not a file)

Default to `[]` if the key’s value is falsey
Hm, shouldn't need that call to 'rescue' in Site#whitelist
Refactor conditions for allowing plugins into a new method: Site#plguin_allowed?
Print the output of Jekyll if the command fails
Whoops, it's called 'jekyll_run_output'
I mean the argument and the local variable should be the same thing
Update History.markdown for the 1.4.0 release
Update the site for the 1.4.0 release

Add a release announcement and update the History file
bump the version number in the code
prep the gemspec for 1.4.0
Use YYYY-MM-DD in History file :)
1.4.0 release post fixes
Merge pull request #1785 from mojombo/release-1.4.0-updates
Release 1.4.0