added prerequisites
modified common.js to use WebStorage when it saves scores
modified questionnaire.html to use WebStorage
fixed a bug to make toJSON method return appropriate JSON string
moved rader.js from js directory to lib directory
fixed a bug to make set_result & get_result method work
modified result.html to use WebStorage
modified result.html to save analysis history
Merge branch 'storage'

Conflicts:
	questionnaire.html