Change repoScaleHint to commit count

[styfle]

Before this PR, the hint would show "this seems to be a medium project" which is not very helpful since it already shows medium in the badge.

This PR changes the hint to display the commit count which gives a better idea of why it's ranked as "medium" project.

[lourot]

Awesome, I totally agree, see #159. @brillout I know you actually want to do more in this area but this looks like a good short-term move to me. What do you think?

[lourot]

@styfle by the way a while ago we used to show this data as the amount of non-merge commits (that's why this value is usually a bit lower than the amount of commits displayed on GitHub). You might want to be more precise, or you might prefer to keep this sentence short, I have no strong preference personally.

@brillout validated locally. As far as I'm concerned we can merge :)

[brillout]

Agree as well.

Thanks!