Change store_path() to not clear on-disk file if serialization fails

[nyanpasu64]

Partly resolves #47.

I think this would benefit from a unit test to ensure that a failed serialization doesn't overwrite the file.

[nyanpasu64]

I added a unit test ensuring that if you call store_path() with an object that fails to serialize, the file on disk will not be overwritten or truncated. I added the tempfile dev-dependency. Is this acceptable, or should I hard-code a path under std::env::temp_dir()?

[matthiasbeyer]

Besides this one small remark, I like the changeset here! 🎉

[nyanpasu64]

The review still says it's waiting for changes even though I resolved the conversation. Should this be merged or edited or not?

[matthiasbeyer]

🎉 thanks for your contribution! 😄