Update dataset structure

Adding new files and removing old ones

data/new_train.csv

@@ -0,0 +1,3 @@
+id,feature1,feature2,label
+1,0.5,0.3,A
+2,0.7,0.2,B

data/train.csv

@@ -1,3 +0,0 @@
-id,text,label
-1,hello world,positive
-2,goodbye,negative