Added clarification about DatasetWriter#write having to match partition.
Added clarification about DatasetWriter#write having to match partition.

This is something we should tighten up in the future (PA-38).

bbaugher/kite,bbrownz/kite,tomwhite/kite,bbaugher/kite,joey/kite,andrewrothstein/kite,StephanieMak/kite,joey/kite,megnataraj/kite,kite-sdk/kite,scalingdata/cdk,tinkujohn/kite,prazanna/kite,bbrownz/kite,megnataraj/kite,andrewrothstein/kite,whoschek/kite,gabrielreid/kite,ronanstokes/kite,yuzhu712/cdk,busbey/kite,bbaugher/kite,gabrielreid/kite,mkwhitacre/kite,rbrush/kite,rbrush/kite,cloudera/cdk,yuzhu712/cdk,cloudera/cdk,stevek-ngdata/kite,whoschek/kite,stevek-ngdata/kite,ronanstokes/kite,dlanza1/kite,rdblue/kite,busbey/kite,kite-sdk/kite,scalingdata/cdk,prazanna/kite,busbey/kite,joey/kite,ronanstokes/kite,bbrownz/kite,kite-sdk/kite,StephanieMak/kite,dlanza1/kite,prazanna/kite,EdwardSkoviak/kite,stevek-ngdata/kite,scalingdata/cdk,megnataraj/kite,EdwardSkoviak/kite,yuzhu712/cdk,rdblue/kite,EdwardSkoviak/kite,tinkujohn/kite,andrewrothstein/kite,rdblue/kite,StephanieMak/kite,tinkujohn/kite,tomwhite/kite,mkwhitacre/kite,rbrush/kite,gabrielreid/kite,mkwhitacre/kite