laguerre() degrees seem off

The degree of then first polynomial is marked as 1, but it's a 0 degree polynomial...

``` r
library("mpoly")

laguerre(0:1)
#> Loading required package: polynom
#>
#> Attaching package: 'polynom'
#> The following object is masked from 'package:mpoly':
#>
#> LCM
#> 1
#> -1 x + 1

str(laguerre(0:1))
#> List of 2
#> $ :List of 1
#> ..$ : Named num 1
#> .. ..- attr(*, "names")= chr "coef"
#> ..- attr(*, "class")= chr [1:2] "laguerre" "mpoly"
#> ..- attr(*, "laguerre")=List of 4
#> .. ..$ degree : num 1
#> .. ..$ alpha : num 0
#> .. ..$ indeterminate: chr "x"
#> .. ..$ normalized : logi FALSE
#> $ :List of 2
#> ..$ : Named num 1
#> .. ..- attr(*, "names")= chr "coef"
#> ..$ : Named num [1:2] 1 -1
#> .. ..- attr(*, "names")= chr [1:2] "x" "coef"
#> ..- attr(*, "class")= chr [1:2] "laguerre" "mpoly"
#> ..- attr(*, "laguerre")=List of 4
#> .. ..$ degree : num 1
#> .. ..$ alpha : num 0
#> .. ..$ indeterminate: chr "x"
#> .. ..$ normalized : logi FALSE
#> - attr(*, "class")= chr "mpolyList"
```

^{Created on 2019-03-19 by the [reprex package](https://reprex.tidyverse.org) (v0.2.1)}