Add Dark Zenburn theme (#134)

data/themes.yml

@@ -174,3 +174,4 @@
 - { colors: '#93C4D3,#FFFFFF,#93C4D3,#FFFFFF,#FFFFFF,#173C4C,#66CC33,#173C4C', name: 'Waze'}
 - { colors: '#131313,#424242,#424242,#BDC3C7,#424242,#bdc3c7,#2ecc71,#e74c3c', name: 'Zebra'}
 - { colors: '#1B1C5B,#1B1C5B,#8E3441,#FFFFFF,#914751,#FFFFFF,#2ACB46,#F5804F', name: 'The Incomparable'}
+- { colors: '#333333,#1E2320,#709080,#FFFFFF,#1E2320,#FFFFFF,#F0DFAF,#CC9393', name: 'Dark Zenburn'}