Final adjustments to SLIME Trace Dialog before documentation update.

* contrib/slime-trace-dialog.el (slime-trace-dialog): simplify contrib
definition.
(slime-trace-dialog-mode): Also activate
`slime-trace-dialog-minor-mode'.
(slime-trace-dialog-minor-mode): New minor mode.
(slime-trace-dialog--menubar): New single top-level menu for
`slime-trace-dialog-minor-mode'.
(slime-trace-dialog-after-toggle-hook): New hook.
(slime-trace-dialog-toggle-trace): Run hooks.
(slime-trace-dialog-toggle-complex-trace): New interactive
function for calling from the menu.
(slime-trace-dialog--easy-menu): Delete it.
(my-menu): Delete it.
Previous commit broke the Trace Dialog's lighter menu in the modeline.

* contrib/slime-trace-dialog.el (slime): Remove redundant
`eval-and-compile'
(slime-trace-dialog-mode): Don't also activate
`slime-trace-dialog-minor-mode'.
(slime-trace-dialog--menubar): Define same menu for both minor and
major modes.
State some things explicitly.
* lib/.nosearch: New file.  (github issue#115)
Document the SLIME Trace Dialog in the manual

* doc/slime.texi (SLIME Trace Dialog): New section.
Correct install-info dependencies in doc/Makefile

* doc/Makefile (install-info): only set $section when making
"install-info".
Use a style file when generating HTML documentation.

* doc/Makefile (slime.html): Use --css-include=slime.css

* doc/slime.css: New file. Simple stylesheet adapted from the one
used by Maxima (http://maxima.sourceforge.net/).
Closes #5: website and documentation out of date

* README.md: Add link to manual in github pages (hosted under
capitaomorte.github.io for now).