Slug length can be MaxLength+1

[Romain Poirot]

When using the truncate function, the slug can be longer than MaxLength on specific conditions. See this example:

• original string (of length 11): "abcde-fghij"
• MaxLength: 10
• expected string: "abcde"
• output string: "abcde-fghij"

Current function fails on this edge case because the last word doesn't end with a "-" during the max length test here so the - 1 is wrongfully applied.

[Dobrosław Żybort]

@Redlinkk Thank you for catching this, I added more tests, fixed one more problem and merged it. Now it's part of v1.13.0 release.

[Aymen Ben Tanfous]

I actually found another case I described here #76