Add instructions on recording big data files in revised reproduction package

[abogdanoski]

To add in Improvements section:
If you think that your reproduction package will exceed this limit please do the following:

• Separate your reproduction package in two: (1) data and (2) code and documentation.
• Post the second one in a trusted repository.
• For the data reproduction package identify all the files that are different from the original reproduction package and upload only those. For example, suppose the original repro package has data/raw_data1.csv, data/clean_data/data_set1.dta. If you modify only the file data_set1.dta, then upload a revised reproduction package that has the same folder structure but only the files that differ: data/clean_data/data_set1.dta. If you want to make it even more clear you could add a readme file describing the modified files.

[fhoces]

added here