Keep snippet vars definitions in a single format across all snippets and documentation.

The format is:

# var-name: value

Previously snippets used a mixture of the following formatting:

#var-name: value
#var-name : value
# var-name: value
# var-name : value

snippets/snippet-mode/vars

@@ -1,12 +1,12 @@
 # -*- mode: snippet -*-
-# name : Snippet header
-# contributor : joaotavora
+# name: Snippet header
+# contributor: joaotavora
 # key: vars
 # --
-# name : $1${2:
-# key : ${3:trigger-key}}${4:
-# keybinding : ${5:keybinding}}${6:
-# expand-env : (${7:})}
-# contributor : $6
+# name: $1${2:
+# key: ${3:trigger-key}}${4:
+# keybinding: ${5:keybinding}}${6:
+# expand-env: (${7:})}
+# contributor: $6
 # --
 $0