Environs

- Minor optimization.

Bug fixes:

- Reset prefix when an exception is raised within an `env.prefixed()`
context ([78](https://github.com/sloria/environs/issues/78)).
Thanks [rcuza](https://github.com/rcuza) for the catch and patch.

Bug fixes:

- Fix behavior when passing a `dict` value as the default
to `env.dict` ([76](https://github.com/sloria/environs/pull/76)).
Thanks [c-w](https://github.com/c-w) for the PR.

Support:

- Document how to read a specific file with `env.read_env`
([66](https://github.com/sloria/environs/issues/66)).
Thanks [nvtkaszpir](https://github.com/nvtkaszpir) and
[c-w](https://github.com/c-w).

Bug fixes:

- Fix compatibility with marshmallow 3.0.0>=rc6.

Bug fixes:

- Fix accessing proxied envvars when using `env.prefixed`
([72](https://github.com/sloria/environs/issues/72)).
Thanks [Kamforka](https://github.com/Kamforka) for the catch and patch.
- Fix behavior when an envvar is explicitly set to an empty string
([71](https://github.com/sloria/environs/issues/71)).
Thanks [twosigmajab](https://github.com/twosigmajab) for reporting
and thanks [hvtuananh](https://github.com/hvtuananh) for the PR.

- `EnvError` subclasses `ValueError` ([50](https://github.com/sloria/environs/pull/50)).
Thanks [alexpirine](https://github.com/alexpirine).
- Test against Python 3.7.

- Use python-dotenv for parsing .env files. `Env.read_env` behaves
mostly the same except that a warning isn't raised by default if a
.env file isn\'t found. Pass `verbose=True` to raise a warning.