Bump elixir version to ~> 1.8

CHANGELOG.md

@@ -16,6 +16,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Remove `Reply-To` header from report emails for admins.
 
 ### Changed
+- **Breaking:** Now pleroma requires Elixir ~> 1.8 (it was ~> 1.7)
 - **Breaking:** Configuration: A setting to explicitly disable the mailer was added, defaulting to true, if you are using a mailer add `config :pleroma, Pleroma.Emails.Mailer, enabled: true` to your config
 - **Breaking:** Configuration: `/media/` is now removed when `base_url` is configured, append `/media/` to your `base_url` config to keep the old behaviour if desired
 - **Breaking:** `/api/pleroma/notifications/read` is moved to `/api/v1/pleroma/notifications/read` and now supports `max_id` and responds with Mastodon API entities.

mix.exs

@@ -5,7 +5,7 @@ def project do
     [
       app: :pleroma,
       version: version("1.0.0"),
-      elixir: "~> 1.7",
+      elixir: "~> 1.8",
       elixirc_paths: elixirc_paths(Mix.env()),
       compilers: [:phoenix, :gettext] ++ Mix.compilers(),
       elixirc_options: [warnings_as_errors: true],