[MRG] pin needletail version to keep MSRV at 1.37

[luizirber]

Needletail 0.4.1 uses the matches! macro, which was added on Rust 1.42. Since it is a dev-only dep, I'm pinning it to 0.4.0 until we bump our minimum supported Rust version to 1.42.

Checklist

• Is it mergeable?
• make test Did it pass the tests?
• make coverage Is the new code covered?
• Did it change the command-line interface? Only additions are allowed
  without a major version increment. Changing file formats also requires a
  major version number increment.
• Was a spellchecker run on the source code and documentation after
  changes were made?

[codecov]

Codecov Report

Merging #1393 (6d45a50) into latest (b866935) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           latest    #1393   +/-   ##
=======================================
  Coverage   89.15%   89.15%           
=======================================
  Files         123      123           
  Lines       18596    18596           
  Branches     1433     1433           
=======================================
  Hits        16580    16580           
  Misses       1780     1780           
  Partials      236      236           

Flag	Coverage Δ
python	94.41% <ø> (ø)
rust	67.37% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update b866935...6d45a50. Read the comment docs.