[#75] Add test for login and logout

Add webmock, capybara and rspec-rails to app
Fix typo in session controller
Prepare spec_helper for tests
[#75] Add user tests

Add tests for create user
Add tests for update user
Add test for delete user
Add tests for show user
Move capybara gem to test group
Fix users controller create with invalid params
Fix typo in views/users/new
Unify tests messages
[#75] Change test indentation and messages
[#75] Unify hash style
Merge pull request #40 from gotar/user_tests

User tests