Date attribute parameter check generates false positive

QA test creates a false positive in https://github.com/cyrealtype/Lora-Cyrillic/pull/15/commits/02e0832158842a940f68d965f2283a1e507ddaa1
```
================================================================================
FAIL: Check all .glyph files share same parameters
--------------------------------------------------------------------------------
Files do not have equal attribute parameters.

Lora-Italic.glyphs date: 2017-10-27 16:56:35 +0000
Lora.glyphs date: 2017-10-27 16:55:49 +0000
```

Start with the QA test shown in the issue and inspect the linked commit for how date attributes are compared. Reproduce the reported failure, then verify that the test distinguishes meaningful parameter differences from the differing dates without reporting this case as a false positive.

Written by the indexing model from the issue text.