Enable (show-paren-mode) the right way

(show-paren-mode) is a global minor mode. It should be enabled only
once.
Refine `ggtags' settings

* Call (push-mark) before jumping.
* Use default ggtags keybindings.
Refine `elisp-slime-nav' settings

* Call (push-mark) before jumping.
Add package `mark-tools`

Use M-x list-marks to show the positions in `global-mark-ring'
Refine jedi settings

* Fix install information about external packages
* Move jedi settings to the top level
* Defer variable settings