remove git submodules
Squashed 'ext/http-parser/' content from commit 6df37aa

git-subtree-dir: ext/http-parser
git-subtree-split: 6df37aa52d7063a5dde0c86b5b0c992756b67577
Merge commit '8af20325c37cfb129e4601357f0718cb411c6e85' as 'ext/http-parser'
Squashed 'ext/multipart-parser-c/' content from commit 0d217a0

git-subtree-dir: ext/multipart-parser-c
git-subtree-split: 0d217a048d87ac7b9d095bd5583a592785dbb2eb
Merge commit '4551e813175eab783abb13e60e09a36f401624f2' as 'ext/multipart-parser-c'
Merge branch 'migrate-to-git-subtree'