Setting axes to integer values in 'ggplot2'

The problem I stumbled across this problem as a TA for an introductory R course. It was a minor question on a Problem Set focussed on creating a Shiny app that the instructor had seeminly dismissed as trivial and not bothered to include in his solution guide. Anyways, I needed to be able to grade the problem set, so I gave it a shot. Like any good programmer, I Googled the question and clicked on the most appealing Stack Overflow response.

Find the intersection of overlapping histograms in R

How to find the point where two histograms overlap.

ggasym ("gg-awesome")

'ggasym' (pronounced "gg-awesome") plots a symmetric matrix with three different fill aesthetics.