Update conditional pyreadline3 dependency for Win

[KyleKing]

Fixes#1025

[KyleKing]

The Azure Pipeline tests appear to be failing due to a HTTP 400 on uploading the codecov report. Otherwise those tests pass

==> Uploading
.url https://codecov.io
.query commit=b45d3d92c536317c47203250924dc080ed659cdf&branch=HEAD&package=py2.1.11
Gzipping contents..
Compressed contents to 14885 bytes
Pinging Codecov...
Error: HTTP 400
Please provide the repository token to upload reports via `-t :repository-token`

I'll look into and fix the AppVeyor build, which reported an error that readline was undefined

[codecov]

Codecov Report

Merging #1046 (a96c0f5) into master (44eb9d4) will not change coverage.
The diff coverage is 100.00%.

@@ Coverage Diff @@## master #1046 +/- ##
=======================================
Coverage 97.92% 97.92% =======================================
Files 22 22 Lines 4619 4619 =======================================
Hits 4523 4523 Misses 96 96 

Impacted Files	Coverage Δ
cmd2/rl_utils.py	100.00% <100.00%> (ø)

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[KyleKing]

I think this is ready for review! I collapsed the commit into a single one

Let me know if you want me to make any changes

(Also I'm not sure if continuous-integration/appveyor/branch will run? I left it for 24 hours with my initial commits before compacting the changes into one and it didn't update)

[tleonhardt]

We should update the CHANGELOG, but that can be done after this merges in

[tleonhardt]

Thanks for the PR @KyleKing !