Broken link to US gov employment projects in 3.2.1

[azpoliak]

The link in

textbook/content/chapters/03/2/1/Growth.ipynb

Line 9 in 6031b7c

"The relationship between two measurements of the same quantity taken at different times is often expressed as a *growth rate*. For example, the United States federal government [employed](http://www.bls.gov/opub/mlr/2013/article/industry-employment-and-output-projections-to-2022-1.htm) 2,766,000 people in 2002 and 2,814,000 people in 2012. To compute a growth rate, we must first decide which value to treat as the `initial` amount. For values over time, the earlier value is a natural choice. Then, we divide the difference between the `changed` and `initial` amount by the `initial` amount."

goes to a dead page. The correct link is https://www.bls.gov/opub/mlr/2013/article/industry-employment-and-output-projections-to-2022.htm