tune up Candidate/Interview pages

1 support assign job opening in new candidate page
2 change column for candidates list page
3 support some column ording for cadidates list page
4 support interviews' pagination

Signed-off-by: Henry Chen <hchen@vmware.com>
Merge branch 'master' of https://github.com/vmw-tmpst/heroapp-LetsHire into interview

Signed-off-by: Henry Chen <hchen@vmware.com>

Conflicts:
	app/assets/javascripts/candidates.js
Merge pull request #196 from Henry-CF/interview

tune up Candidate/Interview pages