Adds thiserror, Display and bumps version

[matthiasdebernardini]

This change makes it easier to consume the crates error for others

[matthiasdebernardini]

    Finished test [unoptimized + debuginfo] target(s) in 0.25s
     Running unittests src/lib.rs (target/debug/deps/xyzpub-d8a7759debd6c883)

running 7 tests
test xyzpubtests::err_when_too_few_bytes ... ok
test xyzpubtests::err_when_too_short ... ok
test xyzpubtests::xpub_not_valid ... ok
test xyzpubtests::xpub_to_tpub ... ok
test xyzpubtests::xpub_to_zpub ... ok
test xyzpubtests::zpub_to_xpub ... ok
test xyzpubtests::xpub_to_ypub ... ok

test result: ok. 7 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s

   Doc-tests xyzpub

running 1 test
test src/lib.rs - (line 8) ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.15s

all tests pass on my machine