fred-gdp-wage.ipynb: Fix #2 by v5, p6.16.0428 upgrades

The notebook code is now Python 2.7 and 3 compatible.
Some minor changes in the econometrics due to new
additional data since December 2014i (two more years of data).

Appendix 3 modified to use time-variant multiplier
which is trend based.

The typography and LaTeX have improved dramatically
in Jupyter markdown cells over older IPython format.

Summary posted at the top.