Allow flate2 >1.0.14

[mbrubeck]

flate2 was pinned to versions <= 1.0.14 in #175, because flate2 1.0.15 updated to miniz_oxide 0.4, which accidentally increased its MSRV (#170, Frommi/miniz_oxide#85).

This was fixed in miniz_oxide 0.4.2 (Frommi/miniz_oxide#95), so all published versions of flate2 can once again be built with Rust 1.34.0.

Note: Since flate2 still has a more lax MSRV policy than zip, we could make a more conservative change that limits the dependency to versions that are known to work on Rust 1.34:

-flate2 = { version = "1.0.0, <=1.0.14", default-features = false, optional = true }
+flate2 = { version = "1.0.0, <=1.0.20", default-features = false, optional = true }

However, I think it would be better, if this breaks again in the future, to fix CI builds by checking in or generating a Cargo.lock file for use in MSRV testing.

[LPGhatguy]

Hello, is there be any way I can help get this merged and released soon?

I recently tried added a dependency on zip that resulted in my crate graph being unresolvable. I have other dependencies in my project that depend on flate2 with version range ^1.0.18. This makes even cargo update fail!

Overall, maximum version ranges like this make me very sad in libraries. Without very careful maintenance, they can result in a library being unadoptable if the rest of the ecosystem has moved on.

[Plecra]

Cheers! This is long overdue 😄