Print database path in errors

[TimoFreiberg]

I had zoxide 0.1.1 installed and encountered the database corruption issue described in #68.
I installed the new version and received the following error message:

Error: could not deserialize old database

Caused by:
    io error: failed to fill whole buffer

I think zoxide should document the default database locations and also print the database file path when it can't be read.

[ajeetdsouza]

That's a valid point, I've been looking into this too. It is documented in the README under _ZO_DATA_DIR, but I suppose it isn't very noticeable. The database location is decided by this function.

[TimoFreiberg]

I found that but it didn't help me in my case, the file I had to delete was ~/.zo, which I only found out via #68 :)

[TimoFreiberg]

Looking at the current master, the specific failure I encountered is no longer there and I didn't find any places where the path was missing from context calls at a cursory glance, so I think this can be closed

[ajeetdsouza]

@TimoFreiberg yes, I've been working on improving zoxide's error messages. Hopefully, such confusions will not happen in future!