adds pretender gem #24
adds dropdown list of users #24
adds dropdown list of users #24
adds impersonate routes #24
changes routes to get #24
adds named post routes #24

also has test code for showing impersonated user
routes, controller and form for pretender work #24
moves login links to nav bar

removes turbo links, removes paragraph from auth_links partial
adds link to add book #24
Layout cleanup

Move impersonate links to sidebar and use partial; Move logged in as
user to sidebar and use partial
specs and admin status helper #24

comment out redundant tests; add helper to display admin status;