Revert "Zero-copy mapcache output when creating response `Buffer`"

This reverts commit 7077bd825097129876be6dd455d913e2dffd2b5c.

The commit passed the tests on the development machine but failed on
Travis-CI: it needs more investigating.
Support the new mapcache cmake build system
Added `tools/git-bisect-run.sh` for regression testing against mapcache
Updated the README
Temporarily hide failing tests

This is pending the resolution of mapserver/mapcache#70