Move color and font theme selection to demo.tex

The `mtheme` is compatible with other colour themes and (technically) other font themes. Moving these declarations to the .tex file makes it easier for the user to use a custom colour theme or to compile the slides on a computer without Fira Sans.

beamerthemem.sty

@@ -57,9 +57,6 @@
 \usetikzlibrary{backgrounds}
 \usetikzlibrary{calc}
 
-\usecolortheme{metropolis}
-\usefonttheme{metropolis}
-
 %}}}
 %{{{ --- Titlepage --------------------
 

demo.tex

@@ -1,6 +1,8 @@
 \documentclass[10pt, compress]{beamer}
 
 \usetheme{m}
+\usecolortheme{metropolis}
+\usefonttheme{metropolis}
 
 \usepackage{booktabs}
 \usepackage[scale=2]{ccicons}