- Add .mix.exs
- `$ mix format`

```
❯ elixir --version
Erlang/OTP 22 [erts-10.5.3] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] [hipe]

Elixir 1.9.2 (compiled with Erlang/OTP 22)

~/src/erl2ex master* ⇡
❯ mix test
Excluding tags: [:e2e, :dummy]

........................................*......................................................................********..........................

Finished in 1.2 seconds
153 tests, 0 failures, 8 excluded, 9 skipped

Randomized with seed 1895

❯ asdf shell elixir 1.8.2

❯ elixir --version
Erlang/OTP 22 [erts-10.5.3] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] [hipe]

Elixir 1.8.2 (compiled with Erlang/OTP 20)

❯ mix test
Compiling 22 files (.ex)
Generated erl2ex app
Excluding tags: [:e2e, :dummy]

........................................*......................................................................*............*******..............

Finished in 1.2 seconds
153 tests, 0 failures, 8 excluded, 9 skipped

Randomized with seed 155934

❯ asdf shell elixir 1.7.4

❯ elixir --version
Erlang/OTP 22 [erts-10.5.3] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] [hipe]

Elixir 1.7.4 (compiled with Erlang/OTP 19)

❯ mix test
Compiling 22 files (.ex)
Generated erl2ex app
Excluding tags: [:e2e, :dummy]

..........................................*....................................................................*******.......*...................

Finished in 1.1 seconds
153 tests, 0 failures, 8 excluded, 9 skipped

Randomized with seed 39178

❯ asdf shell elixir 1.6.6

❯ elixir --version
Erlang/OTP 22 [erts-10.5.3] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] [hipe]

Elixir 1.6.6 (compiled with OTP 19)

❯ mix test
Compiling 22 files (.ex)
Generated erl2ex app
Excluding tags: [:e2e, :dummy]

........................................................................................................................................

Finished in 1.0 seconds
153 tests, 0 failures, 17 skipped

Randomized with seed 991019

❯ asdf shell elixir 1.5.3

❯ asdf shell erlang 18.3.4.9

❯ rm -rf _build

❯ elixir --version
Erlang/OTP 18 [erts-7.3.1.4] [source] [64-bit] [smp:8:8] [async-threads:10] [hipe] [kernel-poll:false]

Elixir 1.5.3

❯ mix test
Compiling 22 files (.ex)
Generated erl2ex app
Excluding tags: [:e2e, :dummy]

........................................................................................................................................

Finished in 1.0 seconds
153 tests, 0 failures, 17 skipped

Randomized with seed 543499

❯ asdf shell elixir 1.4.5

❯ elixir --version
Erlang/OTP 18 [erts-7.3.1.4] [source] [64-bit] [smp:8:8] [async-threads:10] [hipe] [kernel-poll:false]

Elixir 1.4.5

❯ mix test
Compiling 22 files (.ex)
Generated erl2ex app
Excluding tags: [:e2e, :dummy]

........................................................................................................................................

Finished in 1.2 seconds
153 tests, 0 failures, 17 skipped

Randomized with seed 869058
```

Make pass test on all supported elixir versions