Extract canvas_http into seperate gem.

Change-Id: Ib90c12b99d30853a0a1a0235c9aa1b5dd645f614
fixes: CNVS-11949
Reviewed-on: https://gerrit.instructure.com/32176
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Simon Williams <simon@instructure.com>
Reviewed-by: Stanley Stuart <stanley@instructure.com>
QA-Review: August Thornton <august@instructure.com>