fix #1

[holtzermann17]

One line doc fix so that installation requirements are clear. I've verified that this works!

$ make
./xeslatex thesis.tex
Petite Chez Scheme Version 9.5.1
Copyright 1984-2017 Cisco Systems, Inc.

> SLaTeX v. 20090928
typesetting code[microtype.sty][ccicons.sty][xspace.sty][natbib.sty][hyphenat.sty][amsmath.sty][alltt.sty][amssymb.sty][amsfonts.sty][verbatim.sty][url.sty][float.sty][.sty][.sty][comment.sty][fontspec.sty][hanging.sty][xltxtra.sty][makeidx.sty][.sty][fancyvrb.sty][rotating.sty][multicol,ragged2e.sty]......................................................................

[...]

(./fernsimpl.aux) (./related.aux) (./future.aux) (./conclusion.aux)
(./helpers.aux) (./pmatch.aux) (./matche.aux) (./enginesappendix.aux)
(./akinferparserappendix.aux)) )
(see the transcript file for additional information)
Output written on thesis.pdf (198 pages).
Transcript written on thesis.log.