1996-2013 networks and animation

Added code for extracting the networks in all time periods, and getting
the complete network animation 1996-2013
Made project reproducible from 00_main.R

Changed file names and initial settings such as setwd() in .R files so
that the whole project can be launched and reproduced from 00_main.R.
Final video settings

Edited network.video.R to tweak the final video settings and the final
ffmpeg command.
Corrected prop authors in discipline.graph.02.R

Corrected the way the number of top authors to keep in each discipline
is determined as a proportion of the total (had forgotten to do a merge
of authors from the 2 disciplines first).
Final static plots

Added script to produce final static plots.
Minor cosmetic edits to .R files

Also added *.rda and /Submission/ to .gitignore.