mix escriptize: Only include .beam and .app files from ebin.

Fixes #768.
Provide iex -S mix instead of mix iex

In order for iex to work reliably, we need it to pass special
parameters to the Erlang VM. Therefore, it cannot be started
via a regular Elixir script, as in `mix iex`.

Therefore, we need to use `iex -S mix` which first boots iex
and then run the given mix commands.

Closes #692
Merge pull request #777 from alexrp/master

mix escriptize: Only include .beam and .app files from ebin.
Ensure File.cwd works with utf-8 file names
String.capitalize now considers Unicode's titlecase property
Check if native name encoding is utf8
Properly invoke mix on tests
Update LICENSE
The AST now allows metadata to be attached to each node

This means the second item in the AST is no longer an integer
(representing the line), but a keywords list. Code that relies
on the line information from AST or that manually generate AST
nodes need to be properly updated.
Aliases for defmodule also works for raw atoms
Properly expand var! second argument
Improve var! docs
Provide an endpoint for translating elixir forms
Fix type in deprecation
Export elixir:translate_forms/3
Raise an exception if var!(x) does not expand to a proper var
Add hygienic imports to macros
Bump to 0.8.0.dev
Add a system_services_timeout app env var to Elixir.
Use system_services_timeout for elixir_code_server calls in elixir_compiler.