Log curl error.
Add changelog for 0.16.0.
Bump version to 0.16.0.

Changes:

* Chain packager. (smasset)
* Add show-depends CLI option. (unakatsuo)
* Add fpm-cookery chain packager gem recipes. (smasset)
* Compatibility fixes for the latest FPM releases. (skiold)
* Fix problems with tar files that contain no directories. (narkisr)
* New CLI options parsing backend. (using clamp)

Fixes #47