Debian install docs issues

The install instructions on https://www.pgcli.com/install don't match the install instructions on this repo's readme. On this repo it lists the dependencies as:

```
sudo apt-get install python-dev libpq-dev libevent-dev
```

on the website it lists the dependencies as:

```
sudo apt-get install libpq-dev python-dev # debian
```

Also when I try to install `python-dev` I get this error which I resolved by moving to `python-dev-is-python3`:

```
apt install python-dev
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Package python-dev is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
However the following packages replace it:
python-dev-is-python3

E: Package 'python-dev' has no installation candidate
```

Aside from these minor issues the tool is great and thank you for it!

比较 repository README 中的 Debian 依赖命令与 https://www.pgcli.com/install 上的安装说明，然后核实 issue 中报告的当前 Debian 软件包名称。当两处文档都提供一致且可正常工作的 Debian 安装指导时，工作即告完成。

由索引模型根据 Issue 内容生成。