Bump version to 1.3.0

Author: FelonEkonom

README.md

@@ -94,7 +94,7 @@ Apart from plugins, Membrane has stream formats, which live in `membrane_X_forma
 The API for creating pipelines (and custom elements too) is provided by [membrane_core](https://github.com/membraneframework/membrane_core). To install it, add the following line to your `deps` in `mix.exs` and run `mix deps.get`
 
 ```elixir
-{:membrane_core, "~> 1.2"}
+{:membrane_core, "~> 1.3"}
 ```
 
 **Standalone libraries**

mix.exs

@@ -1,7 +1,7 @@
 defmodule Membrane.Mixfile do
   use Mix.Project
 
-  @version "1.2.7"
+  @version "1.3.0"
   @source_ref "v#{@version}"
   @hex_packages_path "scripts/elixir/hex_packages.exs"