Merge pull request prometheus#133 from prometheus/fish-http-config-ex…

…pose-keepalive

Expose DisableKeepAlives in HTTPClientConfig

Implement common file server to return consistent Content-Type (prome…

…theus#191)

* Implement common file server to return consistent Content-Type

When `/etc/mime.types` has a unusual mime type, Content-Type of response becomes the type and you may get unexpected result.
This server returns consistent Content-Type header for js and css files

Signed-off-by: mrasu <[email protected]>

config: extend validity of testdata certs (prometheus#186)

Signed-off-by: Simon Pasquier <[email protected]>