fix: Propagate hyper_util errors

[spiderbiggen]

closes #263

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Project coverage is 63.33%. Comparing base (0bdd50f) to head (e6c3cbc).

Files	Patch %	Lines
src/error.rs	0.00%	3 Missing :warning:
src/session.rs	0.00%	1 Missing :warning:

Additional details and impacted files

| [Files](https://app.codecov.io/gh/jonhoo/fantoccini/pull/267?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Jon+Gjengset) | Coverage Δ | | |---|---|---| | [src/session.rs](https://app.codecov.io/gh/jonhoo/fantoccini/pull/267?src=pr&el=tree&filepath=src%2Fsession.rs&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Jon+Gjengset#diff-c3JjL3Nlc3Npb24ucnM=) | `73.58% <0.00%> (-0.12%)` | :arrow_down: | | [src/error.rs](https://app.codecov.io/gh/jonhoo/fantoccini/pull/267?src=pr&el=tree&filepath=src%2Ferror.rs&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Jon+Gjengset#diff-c3JjL2Vycm9yLnJz) | `24.06% <0.00%> (-0.40%)` | :arrow_down: |

[jonhoo]

Releasing in https://github.com/jonhoo/fantoccini/pull/268