Upgrade juniper_codegen dependencies

[djc]

No description provided.

[codecov-io]

Codecov Report

Merging #231 into master will decrease coverage by 2.59%.
The diff coverage is 0%.

@@            Coverage Diff            @@
##           master     #231     +/-   ##
=========================================
- Coverage   89.88%   87.29%   -2.6%     
=========================================
  Files          95       96      +1     
  Lines       17945    13943   -4002     
=========================================
- Hits        16130    12171   -3959     
+ Misses       1815     1772     -43

Impacted Files	Coverage Δ
juniper_codegen/src/lib.rs	6.25% <ø> (ø)	⬆️
juniper_codegen/src/derive_enum.rs	0% <0%> (ø)	⬆️
juniper_codegen/src/derive_input_object.rs	0% <0%> (ø)	⬆️
juniper_codegen/src/derive_object.rs	0% <0%> (ø)	⬆️
.../src/validation/rules/arguments_of_correct_type.rs	90.46% <0%> (-8.84%)	⬇️
...per/src/validation/rules/fields_on_correct_type.rs	90.9% <0%> (-8.69%)	⬇️
juniper/src/validation/rules/scalar_leafs.rs	91.46% <0%> (-8.54%)	⬇️
juniper/src/tests/schema.rs	70.83% <0%> (-7.74%)	⬇️
...validation/rules/default_values_of_correct_type.rs	92.3% <0%> (-7.7%)	⬇️
.../src/validation/rules/possible_fragment_spreads.rs	93.03% <0%> (-6.97%)	⬇️
... and 73 more

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[LegNeato]

For all these extend(), can you change them to TokenStream::from()? The old code assigned/replaced and the new code extends/appends. While currently they end up being equivalent, let's preserve the old semantics.

[LegNeato]

Thanks for this PR! I was dragging my feat on this and love that you came up with a PR. 🎉

[djc]

So I changed the initial upgrade commit to keep the structure as before (because you're correct that is the minimal change), but then also added a commit that changes the code to the (simpler, in my mind) direct extend structure again. Feel free to skip that commit if you disagree it's an improvement. Also fixed some typos I found during the fixes.

[LegNeato]

Thanks! New changes look good to me.

It looks like due to the regex bump CI fails on Rust 1.21. I think it is worth getting to regex 1.0 and we still work on Rust 1.22 which was released a year ago...so I'm fine dropping 1.21 for this.

The choice is up to you: remove the regex bump from this PR or remove 1.21 from CI, add 1.23, and add a note to the README and CHANGELOG about new minimum rust requirement.

[djc]

Replaced 1.21 with 1.23 for Travis CI and added a note to the changelog about it. I couldn't find any mention of the minimum supported Rust version in README, so I left that for now -- would be happy to do a follow-up, though.