Previously, if `gG` (the recall mapping) was pressed before previously
having pressed a `G` command, the following error would appear:

    Error detected while processing function grappele#Recall:
    line    1:
    E121: Undefined variable: s:line
    E116: Invalid arguments for function grappele#Grappele

This happened because no previous `G` location had been saved.

Displaying an error here makes for a bad user experience. Instead if
this happens, we should just do nothing. To prevent the error, check for
the existence of the `s:line` variable before trying to use it.

Previously, we would save the location of the `G` command regardless of
whether it was used with a count or not. Thus, `34G` and `G` would both
save locations.

Saving the location of `G` isn't really useful, but it's easily
accessed. Instead, only save location when using a count with `G`. This
allows the Grappele command to be useful even after having pressed `G`.

* Update CHANGELOG
* Increment version number in help file

Turns out that invoking `G` wouldn't push your movement to the jumplist
(unlike Vim's real `G`). This was not only confusing, it was also wrong.
Just an oversight on my part that I didn't notice until now.

* Update version number in help file
* Update CHANGELOG

Don't output the mapping result in the command line when using the `G`
command.

Was handling this prevously with the `<Plug>Grappele` mapping but not
with the new one that I added in
07a75d523eadaf1027aa8bf287256602ad05f97f.

Include information about the initial v0.0.1 release.