Non-existent Function Documentation

There is no man folder of Rd files and the README file is insufficient since valid values for function parameters are not specified.

```r
> converted <- convertFormat(aSingleCellExperiment, from = "sce", to = "seurat")
Error: Unsupported conversion from "sce" to "seurat"
```

Lots of R packages depend on `SeuratObject` input data, so this is an important functionality to be missing.