Update readme.txt

tf/bonsai/readme.txt

@@ -1,3 +1,7 @@
 python train.py --help
 
-This gives you the usage instructiosn.
+This gives you the usage instructions.
+
+The train and test files need to be .npy (numpy arrays)
+The format is: [lbl feats] for each data-point
+The dimension of the .npy array will be [Size, num_feats + 1]