implement sessions contoller
juice
implement sessions for orgs and donors
change _form to _donor_form for donor sign up
update home page with registration and login
add sessions comments in routes
add error handling with invalid login
Add validation for organization model
Merge pull request #40 from spring-peepers-2014/session

Implement sessions for both donors and organizations
Merge pull request #42 from spring-peepers-2014/validations

Add validation for organization model
Fix merge conflict in config/routes.rb