In the novice shell lesson 03-pipefilter, changed sort to sort -n. In the lesson , the "sort" command is used to demonstrate sorting line counts. The lesson as written does not produce the given output on the bash shell (but does on Mac OS X terminal). By adding the -n to sort, the example should behave the same across all platforms.
Merge pull request #538 from mestato/fixing-sort-in-shell-lesson-3

In the novice shell lesson 03-pipefilter, changed sort to sort -n.