Checklist

• [X ] Are you running the latest v2 release? The list of releases is here.
• [X ] Did you check the manual for your release? The v2 manual is here
• [ X] Did you perform a search about this feature? Here's the [Github guide](https://help.github.com/en/github/managing-your-wor

If you try to deserialize a protobuf message without the corresponding schema you get a generic message error message:

[INFO] [record_query::proto_index] Proto descriptor cache is stale; recomputing
Missing input file.
thread 'main' panicked at 'protoc descriptor compilation failed', src/proto_index.rs:60
note: Run with `RUST_BACKTRACE=1` for a backtrace.

It would be nice to g

I was experimenting with adding continuous fuzzing integration with https://fuzzit.dev and I found this crash in the fuzzer:

FUZZER: #1085900	REDUCE ft: 19023 corp: 1838/457Kb lim: 724 exec/s: 4505 rss: 43Mb L: 96/4817 MS: 1 EraseBytes-
FUZZER: panic: unsupported value type *toml.Tree: 
FUZZER: 
FUZZER: goroutine 17 [running, locked to thread]:
FUZZER: github.com/pelletier/go-toml.Fuzz

In various examples the lazy_static! macro from lazy_static v1.0 crate generate the deprecation warning
warning: use of deprecated item 'std::sync::ONCE_INIT': the `new` function is now preferred

The actual version of lazy_static is v1.4 and I'm advising to upgrade the create.

The samples directory is a bit small.

For instance, it could use some shell scripts.
Even a hardcore shell scripter sometimes wants an example.

If I have a TOML file like:

"" = "foo bar"

this will be converted to {"undefined": "foo bar"}

This same issue exists at any level of nesting.

According to the TOML spec an empty quoted key is allowed: https://github.com/toml-lang/toml/blob/master/README.md#user-content-keys

It shows it as discouraged, but still shouldn't be parsed as "undefined"