Use toArray() rather than deprecated raw()
merged branch davedevelopment/guzzle-headers-toarray (PR #108)

This PR was merged into the master branch.

Discussion
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Use toArray() rather than deprecated raw()

Sorry for the mess around, there's no mention of it being deprecated in the API docs, but it does say so in the code.

Commits
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df95541 Use toArray() rather than deprecated raw()