Implementation of S3 method for lme class

S3 method for lme class from nlme package.

**Basic example**
```
library(nlme)
fm1 <- lme(distance ~ age, data = Orthodont)
pander(fm1, summary = TRUE)
fm2 <- lme(distance ~ age + Sex, data = Orthodont, random = ~ 1)
pander(fm2, summary=TRUE)
```