Use period as separator for snapshot builds

A tilde ("~") always sorts first on Debian-based systems while empty
parts are equal to zero (see [1]). Development snapshot builds are named
starting with the most recent tag, so sorting them before that tag is
not desirable.

[1]
https://www.debian.org/doc/debian-policy/ch-controlfields.html#version

.goreleaser.yml

@@ -44,6 +44,6 @@ release:
   prerelease: auto
 
 snapshot:
-  name_template: '{{ .Tag }}~snapshot{{ replace (replace .Date ":" "") "-" "" }}-g{{ .ShortCommit }}'
+  name_template: '{{ .Tag }}.snapshot{{ replace (replace .Date ":" "") "-" "" }}.g{{ .ShortCommit }}'
 
 # vim: set sw=2 sts=2 et :