Updated .gitignore

Now ignores LaTeX output, emacs temporary files and miscellaneous backup files.

Signed-off-by: JP-Ellis <coujellis@gmail.com>
Added example using \foreach

Added an example plot which demonstrates how to use \foreach within a
plot so as to programmatically create a lot of different plots.

Signed-off-by: JP-Ellis <coujellis@gmail.com>