recommend is case sensitive for column name

[vikasgupta78]

The issue is due to case sensitive comparison of column name, input vs what's in config

e.g. following works fine:

./scripts/zingg.sh --phase recommend --conf examples/febrl/config.json --column XYZ

but not ./scripts/zingg.sh --phase recommend --conf examples/febrl/config.json --column xyz

StopWordsRecommender:

if(Arrays.asList(data.columns()).contains(args.getColumn())) {

Above needs to be made case insensitive