Fix compilation issue under OTP 19 (#138)
Fix compilation issue under OTP 19 (#138)

There is an issue with ExMachina when used with OTP 19

```
== Compilation error on file test/support/test_factory.ex ==
** (ArgumentError) argument error
    (stdlib) erl_anno.erl:318: :erl_anno.set(:file, 'nofile', -1)
    (stdlib) erl_parse.yrl:1516: anonymous fn/3 in :erl_parse.map_anno/2
    (stdlib) erl_parse.yrl:1631: :erl_parse.modify_anno1/3
    (stdlib) erl_parse.yrl:1517: :erl_parse.map_anno/2
    (stdlib) erl_lint.erl:703: :erl_lint."-set_file/2-lc$^0/1-0-"/2
    (stdlib) erl_lint.erl:448: :erl_lint.exprs_opt/3
    (stdlib) erl_eval.erl:173: :erl_eval.check_command/
```

By removing the `line: -1` the issue goes away. There is also no warning
when doing this so it can be safely removed.
thoughtbot/ex_machina