remove xml dependency

[abcjjy]

Xml project is dead and cause build failure on MacOS Mojave. Xml parsing is not one of the core functions of requests library. Please remove it or replace it with a better xml library.

[coveralls]

Pull Request Test Coverage Report for Build 11

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.6%) to 95.918%

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Files with Coverage Reduction	New Missed Lines	%
tests/user_tests.lua	2	92.91%

Totals
Change from base Build 9:	-0.6%
Covered Lines:	329
Relevant Lines:	343

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💛 - Coveralls

[JakobGreen]

I am attempting to remove xml and json in 2.0 version since they both seem to be having issues on different platforms and versions of lua. I am doing that work in the 2.0 branch.