The quick and dirty way: Assume the potentiometer is 0 ohms, and set up a resistor divider on both sides of the pot to get 2.8 volts.

http://www.wolframalpha.com/input/?i=5*%28x%2B10000%29%2F%282*x%2B10000%29+%3D+2.8.

Use 3 resistors. one 36.6k, then the pot, then another 36.6k in series. The output will be before the pot, after the first resistor.

The calculations are easy, because you know the two resistors on either side of the pot must be the same to get the 2.5 volt division when the potentiometer is 0 ohms!

Edit: More mathy proof that this should work.

http://www.wolframalpha.com/input/?i=5*%2836666+%2B+x%29%2F%2836666%2B36666%2Bx%29+for+x+%3D+0+to+10000

This is all using simple voltage divider math, if you are not well versed in that side of electronics:

https://en.wikipedia.org/wiki/Voltage_dividerIt gets trickier as you change your boundaries, as your initial condition of assuming the surrounding resistors are the same is no longer true (if you don't start at 2.5 volts). Simply changing those resistors will do the trick though (make sure to run calculations first)!