Fixed training tricks (open-mmlab#26)

Author: xvjiarui

docs/getting_started.md

@@ -132,7 +132,7 @@ Assume that you have already downloaded the checkpoints to the directory `checkp
         checkpoints/pspnet_r50-d8_512x1024_40k_cityscapes_20200605_003338-2966598c.pth \
         4 --out results.pkl --eval mIoU cityscapes
     ```
-   Note: There is some inconsistency between cityscapes mIoU and our mIoU. The reason is that cityscapes average each class with class size by default.
+   Note: There is some gap (~0.1%) between cityscapes mIoU and our mIoU. The reason is that cityscapes average each class with class size by default.
    We use the simple version without average for all datasets.
 
 5. Test PSPNet on cityscapes test split with 4 GPUs, and generate the png files to be submit to the official evaluation server.

docs/tutorials/training_tricks.md

@@ -8,7 +8,7 @@ In semantic segmentation, some methods make the LR of heads larger than backbone
 
 In MMSegmentation, you may add following lines to config to make the LR of heads 10 times of backbone.
 ```python
-optimizer_config=dict(
+optimizer=dict(
     paramwise_cfg = dict(
         custom_keys={
             'head': dict(lr_mult=10.)}))