add helper methods for users sessions
add styling related to navbar and background
adjusted layout to show index, signup/login/logout links
add users controller with new/login/create/logout methods
add view and partials for signup/login
add bcrypt methods to user model
Changes:

-all references to params[:user][:username] to params[:user][:email]
-all references to @user.authenticate to User.authenticate, since this method now lives in the user model, not the controller
-name of #end changed to #logout (may have been done in a previous commit)
all refs to column username are changed to column email
include BCrypt, statement (methods may have been previously committed)
add #user_params to handle Rails 4 need for strong params

-also modded line that generates a new User to call #user_params
add 2 add'l fields for first & last name
shows who is currently logged in
bug fix - allows user to logout now
add red color for error messages
corrected spelling
remove redundant error message code
add div to error message to be able to style nicely
fix error when improperly logging in
I am merging this from upstream into my local repo.

Merge branch 'master' of https://github.com/spring-peepers-2014/TravelBlog into chore/create-signup-login-logout
add routes for basic user signup/login/logout functionality