Close HTTP response bodies

Fixes #285.
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makefile: simplify "fmt" target, and include -s flag
Add test to reproduce issue #306
Images can be removed by short-hand ID. Solves #306.
Merge pull request #305 from fsouza/master

Makefile: simplify "fmt" target
Merge pull request #286 from titanous/285-close-bodies

Close HTTP response bodies
fix code block formatting
Merge pull request #312 from sa2ajj/devenv-doc-fix

fix code block formatting
Merge pull request #288 from titanous/expand-contributing

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