Updating minfi.Rmd, fixing issue #81
Updating minfi.Rmd, fixing issue #81

Addresses issue #81 and other minor issues:

* `pData(rgset)` must be of type `DataFrame` - manually converting as per [minfi issue 174](https://github.com/hansenlab/minfi/issues/174)
* `plotSex()` takes a MethylSet object and operates on its `colData` - converting output of `getSex()` to the `colData` slot of `mset` 
* correcting typos and grammar
genomicsclass/labs,joseffrank/labs,joseffrank/labs,genomicsclass/labs