Don't convert header names to lowercase

[gfloyd]

This is a super minor issue of aesthetics, but since HTTP header names are case insensitive, it would be nice if the header names are preserved as provided in the HAR object. I just think it looks nicer in my documentation to have:

-H 'Authorization: Bearer <Your Token>'

Instead of:

-H 'authorization: Bearer <Your Token>'

[ahmadnassri]

I believe there was a reason they were lowered... primarily to avoid duplication, but I have to confirm first ...

[deepakpathania-zz]

+1

[darrenjennings]

As part of discussion in #83 we will move this forward by not lowercasing headers, not de-duping, and making the code not depend on a lowercases content-type key. Stay tuned for a PR...!

[darrenjennings]

Added a branch with a failing test so we can address this once we get a successful test suite and have more confidence in refactors like this: https://github.com/Kong/httpsnippet/tree/fix/74-dont-lowercase-header-keys

[Blacksmoke16]

This should depend on the HTTP version being used. HTTP/1.1 says header names are case-insensitive while HTTP/2 requires them to be lowercase.

[RolphH]

@darrenjennings when do you expect this (part of #83) to be fixed?