Add Makefile for local site building

With this, just run 'make' and review your changes py pointing your browser to
the _site/ directory.

Signed-off-by: Esben Haabendal <esben@haabendal.dk>
Improve _config.yml with syntax highlighting and a few other things

Signed-off-by: Esben Haabendal <esben@haabendal.dk>
New theme: Slate

Switched to Slate theme from https://github.com/jasoncostello/slate
with a few modifications.

Signed-off-by: Esben Haabendal <esben@haabendal.dk>
Fixup blog post layout

Signed-off-by: Esben Haabendal <esben@haabendal.dk>