Improved --enable, support existing hooks, pass args

Improved the --enable (and --disable) options to work better with
existing post-commit hooks. Also additional args after the --enable
option are passed through to the --capture command within the hook so
that calling;

    lolcommits --enable --animate=5 --fork

would result in the following capture hook

    #!/bin/sh
    lolcommits --capture --animate=5 --fork

The --disable option now only removes any lines mentioning `lolcommits`
from the post-commit hook file.

* removed some TODO notes in bin/lolcommits
* added more features to test enabling the lolcommits hook