Fix Mailer for Job Applications - WIP-327

https://assembly.com/coderwall/wips/327

* Use proper asset helper in mailer template
* Setup Mailers in development to save to file for inspection.
* Minor style adjustments.
There's a strange bug where asset_path won't create the proper path unless `config.action_mailer.asset_host` is prefixed with 'http://'

* with **localhost:3000**: the generated path looks like
 //localhost:3000/uploads/user/resume/3/Britt-Mileshosky-Resume-2014.pdf
* with **http://localhost:3000** the path looks like: 
http://localhost:3000/uploads/user/resume/3/Britt-Mileshosky-Resume-2014.pdf

I don't know if it truly matters in development, but for the sake of completeness I'm going to do `config.action_mailer.asset_host = "http://#{config.host}"`  unless you have another suggestion