Merge branch 'master' of https://github.com/gracaninja/lxmls_guide
Scaped "_" in text

The statement \texttt{en_perline001.txt} broke pdflatex. Scaped the "_" to avoid this
Merge with upstream master

kept changes on pages/bigdata/em.tex
Merge branch 'master' of https://github.com/ramon-astudillo/lxmls_guide