[modules/xrandr] Add module to show attached displays

This modules shows attached displays and their states (on or off).
Future versions of this module will order the icons by the relative
order of the screens (left-to-right) and will allow switching monitors
on and off.

see #19

themes/default.json

@@ -126,6 +126,9 @@
 		}
 	},
 	"caffeine": {
-		"states": { "activated": {"prefix": "   " }, "deactivated": { "prefix": "   " } }
+		"states": { "activated": {"prefix": " caf on " }, "deactivated": { "prefix": " caf off " } }
+	},
+	"xrandr": {
+		"states": { "on": { "prefix": " off "}, "off": { "prefix": " on "} }
 	}
 }

themes/gruvbox-powerline.json

@@ -159,5 +159,8 @@
 	},
 	"caffeine": {
 		"states": { "activated": {"prefix": "   " }, "deactivated": { "prefix": "   " } }
+	},
+	"xrandr": {
+		"states": { "on": { "prefix": "   "}, "off": { "prefix": "   "} }
 	}
 }

themes/powerline.json

@@ -158,5 +158,8 @@
 	},
 	"caffeine": {
 		"states": { "activated": {"prefix": "   " }, "deactivated": { "prefix": "   " } }
+	},
+	"xrandr": {
+		"states": { "on": { "prefix": "   "}, "off": { "prefix": "   "} }
 	}
 }

themes/solarized-powerline.json

@@ -159,5 +159,8 @@
 	},
 	"caffeine": {
 		"states": { "activated": {"prefix": "   " }, "deactivated": { "prefix": "   " } }
+	},
+	"xrandr": {
+		"states": { "on": { "prefix": "   "}, "off": { "prefix": "   "} }
 	}
 }

themes/solarized.json

@@ -152,5 +152,8 @@
 	},
 	"caffeine": {
 		"states": { "activated": {"prefix": " caf on " }, "deactivated": { "prefix": " caf off " } }
+	},
+	"xrandr": {
+		"states": { "on": { "prefix": " off "}, "off": { "prefix": " on "} }
 	}
 }