Preserve original header casing which becomes exposed by getNames().

[alexjeffburke]

Hey,

This probably needs a little more work, but wanted to get started right away.

This commit adds a dictionary that stores the original casing headers were supplied with. getNames() is altered to pull those out, but other places accessing headers are forced to use an explicit lowercase version of the function to avoid behavioural change.

Two things I'm aware may need changing:

• the name of the extra dictionary (currently namesWithCase)
• whether getNamesLowerCase() should be exposed

Cheers, Alex.

[coveralls]

Coverage decreased (-0.1%) to 91.753% when pulling b523c72 on alexjeffburke:feature/preserve-header-casing into 38e40dd on papandreou:master.

[papandreou]

This looks really promising. I think I would have come up with exactly the same implementation :)

[alexjeffburke]

This has been tested against unexpected-messy - there were two cases of direct access to the lowercase names which when addressed allowed the entire test suite to pass as is.

After our quick touch base earlier, if I can get an ack here will start getting these things merged. I guess we're talking semver-minor for these bits to cover our bases?

[alexjeffburke]

Oh and this immediately causes unexpected-mitm to write headers specified using response object syntax with their original case :)

[papandreou]

toString, toJSON, and toCanonicalObject should probably also preserve the casing now that we're able to do it?

Not a blocker, though, so 👍 from me :)