overspecify travis config

Author: kashefy

.travis.yml

@@ -1,5 +1,6 @@
+os: linux
 dist: bionic
-#language: r
+language: ruby
 before_install:
 - sudo apt-get -qq update && sudo apt-get install -qq -y --no-install-recommends texlive-fonts-recommended texlive-latex-extra texlive-fonts-extra dvipng texlive-latex-recommended texlive-science
 #- tlmgr install index

notes/03_kernel-pca/3_kpca.tex

@@ -158,7 +158,6 @@ \subsubsection{The eigenvalue problem}
 
 \end{frame}
 
-
 \mode<article>{
 
 It is possible to arrive at the linear relationship in \eqref{eq:ephi} by substituting \eqref{eq:cov} into the eigenvalue problem in \eqref{eq:eig}: