Request body unreadable

The request body is for some URLs broken and shows unreadable entries.

This is what is logged in terminal and also shown in web interface:
```
�VYo�8�+�Ї�\�����I#�i�$NI۴)���+�ߡ�M��h�X?������7��d�1N�
���%��d>gnp�cd[�Ǎ��T�l�J;�*[H��0
�6��і�`��9�s߸o(y��)�K8��+H�
ʵ4%k���l�~�*`��,#uR��k�c�^�K���Z��[ͺ��S
1�vi�`�F��ڛ���ڿ��wl���!4\�j�A�d�����w�9R���Q��*/~�.t{ҭ~�6�?
�B�}��G��j=�+}�P���Xd�O,�iV4��HY�*���S�H=�~�#R�\
```

Data:
```
General:
Method: POST
URL:https://api.matjaz.com/api/v12/report
Protocol: HTTP/1.1

Header:
Host : api.matjaz.com
Content-Type : application/json
Accept :*/*
Connection : keep-alive
Content-Encoding : gzip
Accept-Language : en-gb
Accept-Encoding : br, gzip, deflate
```

#### Which platform are you running AnyProxy
Platforms: Linux and Mac
Node Version: 8.13.0, 10.13.0

#### The version of the AnyProxy
v4.0.13 and v4.0.12

#### Your expected behavior of AnyProxy
I expect to have a stringified and readable output.

No source file, test, or entry point is identified. Start by reproducing the POST request to the reported URL with its Content-Encoding: gzip header, then trace how AnyProxy logs and displays the request body. Done means the body is decoded into readable text in both the terminal and web interface.

Written by the indexing model from the issue text.