Git merge errors

I have a git branch called 9-sign-in-out with perfectly working code, and I want to turn it into the master. I'm currently on the master branch.

$ git branch
9-sign-in-out
* master

I'm trying to switch to 9-sign-in-out branch, but it doesn't allow me to:

$ git checkout 9-sign-in-out
app/helpers/application_helper.rb: needs merge
config/routes.rb: needs merge
error: you need to resolve your current index first

Any idea how can I ignore all the master branch errors and turn the 9-sign-in-out branch into the master? Maybe git rebase? But I don't want to lose the code in 9-sign-in-out branch.