Added autocompletion support for Elixir mix command

plugins/mix/_mix

+#compdef mix 
+#autoload
+
+# Elixir mix zsh completion
+
+local -a _1st_arguments
+_1st_arguments=(
+    'archive:Archive this project into a .ez file'
+    'clean:Clean generated application files'
+    'compile:Compile source files'
+    'deps:List dependencies and their status'
+    "deps.clean:Remove dependencies' files"
+    'deps.compile:Compile dependencies'
+    'deps.get:Get all out of date dependencies'
+    'deps.unlock:Unlock the given dependencies'
+    'deps.update:Update dependencies'
+    'do:Executes the commands separated by comma'
+    'escriptize:Generates an escript for the project'
+    'help:Print help information for tasks'
+    'local:List local tasks'
+    'local.install:Install a task or an archive locally'
+    'local.rebar:Install rebar locally'
+    'local.uninstall:Uninstall local tasks or archives'
+    'new:Creates a new Elixir project'
+    'run:Run the given file or expression'
+    "test:Run a project's tests"
+    '--help:Describe available tasks'
+    '--version:Prints the Elixir version information'
+)
+
+__task_list ()
+{
+    local expl
+    declare -a tasks
+
+    tasks=(archive clean compile deps deps.clean deps.compile deps.get deps.unlock deps.update do escriptize help local local.install local.rebar local.uninstall new run test)
+
+    _wanted tasks expl 'help' compadd $tasks
+}
+
+local expl
+
+local curcontext="$curcontext" state line
+typeset -A opt_args
+
+_arguments -C \
+    ':command:->command' \
+    '*::options:->options'
+
+case $state in
+  (command)
+      _describe -t commands "mix subcommand" _1st_arguments
+      return
+  ;;
+
+  (options)
+    case $line[1] in
+      (help)
+         _arguments ':feature:__task_list' 
+    esac
+  ;;
+esac
+