Fix compilation log behaviour when compiling definitions

* sly.el (sly-maybe-show-compilation-log): Pass :hidden to
`sly-show-compilation-log' according to compilation success.
(sly-show-compilation-log): Take `select' arg.
Closes #10: Review NEWS.md file

Add some information about the next upcoming alpha release.
Improve sly-sticker's documentation

* contrib/sly-stickers.el (sly-stickers-clear-defun-stickers)
(sly-stickers-clear-buffer-stickers)
(sly-stickers-clear-region-stickers)
(sly-stickers-delete-sticker-at-point)
(sly-stickers-maybe-add-sticker): Add docstring.
(sly-stickers-maybe-add-sticker): Add a hint in the echo area.
(sly-stickers-fetch)
(sly-stickers-compile-region-aware-of-stickers): Add doctring.

* NEWS.md: describe `sly-stickers' a little more.
Preparatory work for sly-stickers buffer compilation support

* sly.el (sly-temp-message): New function.
(sly-compilation-finished-hook): Default value is now a list.

* contrib/sly-stickers.el (sly-stickers): Add to `sly-compilation-finished-hook'
(sly-stickers--disarm-sticker): Disarmed sticker perhaps was never pre-armed.
(sly-stickers-after-buffer-compilation): New function.
SLY contribs are first class citizens, and so are their tests

* Makefile: Reorganize targets to integrate contrib compiling and
testing in a single Makefile.
* contrib/Makefile: Deleted file

* lib/sly-tests.el (sly-auto-test-tags): Adjust tagging heuristic.