update training section with example output and explanation

Author: kevinhughes27

README.md

@@ -40,7 +40,7 @@ to the `./samples` folder:
 6. Use `tools/mergevec.py` to merge the samples in `./samples` into one file:
 
         python ./tools/mergevec.py -v samples/ -o samples.vec
-        
+
    Note: If you get the error `struct.error: unpack requires a string argument of length 12`
    then go into your **samples** directory and delete all files of length 0.
 
@@ -52,8 +52,44 @@ OpenCV, and save the results to `./classifier`:
           -numNeg 600 -w 80 -h 40 -mode ALL -precalcValBufSize 1024\
           -precalcIdxBufSize 1024
 
-8. Wait until the process is finished (which takes a long time — a couple of
-days probably, depending on the computer you have and how big your images are).
+    After starting the training program it will print back its parameters and then start training. Each stage will print out some analysis as it is trained:
+
+      ```
+      ===== TRAINING 0-stage =====
+      <BEGIN
+      POS count : consumed   1000 : 1000
+      NEG count : acceptanceRatio    600 : 1
+      Precalculation time: 11
+      +----+---------+---------+
+      |  N |    HR   |    FA   |
+      +----+---------+---------+
+      |   1|        1|        1|
+      +----+---------+---------+
+      |   2|        1|        1|
+      +----+---------+---------+
+      |   3|        1|        1|
+      +----+---------+---------+
+      |   4|        1|        1|
+      +----+---------+---------+
+      |   5|        1|        1|
+      +----+---------+---------+
+      |   6|        1|        1|
+      +----+---------+---------+
+      |   7|        1| 0.711667|
+      +----+---------+---------+
+      |   8|        1|     0.54|
+      +----+---------+---------+
+      |   9|        1|    0.305|
+      +----+---------+---------+
+      END>
+      Training until now has taken 0 days 3 hours 19 minutes 16 seconds.
+      ```
+
+    Each row represents a feature that is being trained and contains some output about its HitRatio and FalseAlarm ratio. If a training stage only selects a few features (e.g. N = 2) then its possible something is wrong with your training data.
+
+    At the end of each stage the classifier is saved to a file and the process can be stopped and restarted. This is useful if you are tweaking a machine/settings to optimize training speed.
+
+8. Wait until the process is finished (which takes a long time — a couple of days probably, depending on the computer you have and how big your images are).
 
 9. Use your finished classifier!