Allow hyphens in GITHUB_URL

The parsing of the `GITHUB_URL` should support hyphens in host names
to comply with https://tools.ietf.org/html/rfc952 .

Otherwise `gist` will fail to find the corresponding `.gist` token
file if the server contains a hyphen. For example,
`https://github.my-corp.com/`.

Signed-off-by: Lucas Magasweran <[email protected]>

Author: lucasrangit

lib/gist.rb

@@ -44,7 +44,7 @@ class ClipboardError < RuntimeError; include Error end
   module AuthTokenFile
     def self.filename
       if ENV.key?(URL_ENV_NAME)
-        File.expand_path "~/.gist.#{ENV[URL_ENV_NAME].gsub(/:/, '.').gsub(/[^a-z0-9.]/, '')}"
+        File.expand_path "~/.gist.#{ENV[URL_ENV_NAME].gsub(/:/, '.').gsub(/[^a-z0-9.-]/, '')}"
       else
         File.expand_path "~/.gist"
       end