Fix spec for surround_many

Signed-off-by: Eric Meadows-Jönsson <eric.meadows.jonsson@gmail.com>
Fix :stderr_to_stdout option

Signed-off-by: Eric Meadows-Jönsson <eric.meadows.jonsson@gmail.com>
Send elixir version as parameter when installing hex

Signed-off-by: Eric Meadows-Jönsson <eric.meadows.jonsson@gmail.com>