fix: logger should output to stdout

[quake]

resolve https://github.com/nervosnetwork/ckb-light-client/issues/137

[codecov-commenter]

Codecov Report

Patch coverage has no change and project coverage change: -0.05 :warning:

Comparison is base (655aad5) 69.71% compared to head (48efdf1) 69.67%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #138 +/- ## =========================================== - Coverage 69.71% 69.67% -0.05% =========================================== Files 26 26 Lines 6373 6377 +4 =========================================== Hits 4443 4443 - Misses 1930 1934 +4 ``` | Flag | Coverage Δ | | |---|---|---| | unittests | `69.67% <0.00%> (-0.05%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=nervosnetwork#carryforward-flags-in-the-pull-request-comment) to find out more. | [Impacted Files](https://codecov.io/gh/nervosnetwork/ckb-light-client/pull/138?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=nervosnetwork) | Coverage Δ | | |---|---|---| | [src/main.rs](https://codecov.io/gh/nervosnetwork/ckb-light-client/pull/138?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=nervosnetwork#diff-c3JjL21haW4ucnM=) | `9.09% <0.00%> (-5.20%)` | :arrow_down: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=nervosnetwork). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=nervosnetwork)

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