Sanitize user content before creating new idea

[theonlyrao]

Prevents malicious script attack in the form
<script>alert('Hello');</script> from changing JS on the idea index
page using the ActiveRecord sanitize method.

See http://guides.rubyonrails.org/security.html#injection and http://stackoverflow.com/questions/3009023/how-to-sanitize-sql-fragment-in-rails

@martensonbj, @joshuajhun, @rrgayhart, @chadellison

closes #28

[rrgayhart]

No attacks is good for everyone involved - good catch!