Fix font kerning in container

There is a known *issue in Debian distros around subpixel 
hinting & font smoothing. Link below provides a description
& an example font configuration for fixing it.

This was highlighted in the **below wkhtmltopdf issue.

The font configuration(according to the Readme found in
`fonts/config.d/`) relies on ordering hence the `10-` prefix.


*  https://wiki.debian.org/Fonts#Subpixel-hinting_and_Font-smoothing

** wkhtmltopdf/wkhtmltopdf#45

Dockerfile

@@ -9,6 +9,7 @@ RUN rm -rf wkhtmltox
 
 RUN cp -r ./fonts/liberation_sans /usr/share/fonts/truetype/
 RUN fc-cache -f -v
+RUN cp ./fonts/10-wkhtmltopdf.conf /etc/fonts/conf.d/
 
 ENV UNICORN_PORT 3000
 EXPOSE $UNICORN_PORT

README.md

@@ -21,7 +21,8 @@ machine. You can find the relevant fonts in the `fonts/` directory. You should
 be able to add them to OS X by double clicking the font.
 
 The `Dockerfile` is responsible for setting up the fonts from the repo on the
-container.
+container. It also includes a font configuration file required to fix font
+hinting and anti-aliasing in the container when generating PDF's.
 
 ### `Environment Variables`
 

fonts/10-wkhtmltopdf.conf

@@ -0,0 +1,29 @@
+<?xml version='1.0'?>
+<!DOCTYPE fontconfig SYSTEM 'fonts.dtd'>
+<fontconfig>
+ <match target="font">
+  <edit mode="assign" name="rgba">
+   <const>rgb</const>
+  </edit>
+ </match>
+ <match target="font">
+  <edit mode="assign" name="hinting">
+   <bool>true</bool>
+  </edit>
+ </match>
+ <match target="font">
+  <edit mode="assign" name="hintstyle">
+   <const>hintslight</const>
+  </edit>
+ </match>
+ <match target="font">
+  <edit mode="assign" name="antialias">
+   <bool>true</bool>
+  </edit>
+ </match>
+  <match target="font">
+    <edit mode="assign" name="lcdfilter">
+      <const>lcddefault</const>
+    </edit>
+  </match>
+</fontconfig>