Requests+Gevnet trigger SSLERROR when use goproxy

Summary.

## Expected Result
<Response [200]>

## Actual Result
HTTPSConnectionPool(host='www.baidu.com', port=443): Max retries exceeded with url: / (Caused by SSLError(SSLError("bad handshake: Error([('SSL routines', 'ssl3_read_bytes', 'sslv3 alert unexpected message')],)",),))

## Reproduction Steps
```bash
echo "ignore timeout error!"
echo "
import gevent
from gevent import monkey, pool
from gevent.subprocess import Popen, PIPE
monkey.patch_all(select=False)
import requests
requests.packages.urllib3.disable_warnings()
import time
import os

def poc():
    return requests.get('https://www.qq.com:443/', proxies={'http': 'http://127.0.0.1:30000', 'https': 'http://127.0.0.1:30000'},verify=False,timeout=5)

for i in range(10):
    try:
        print(poc())
    except Exception as e:
        print(e)
" > error.py

echo "
import requests
requests.packages.urllib3.disable_warnings()
import time
import os

def poc():
    return requests.get('https://www.qq.com:443/', proxies={'http': 'http://127.0.0.1:30000', 'https': 'http://127.0.0.1:30000'},verify=False,timeout=5)

for i in range(10):
    try:
        print(poc())
    except Exception as e:
        print(e)
" > success.py

python3 error.py
python3 success.py
```
Result:
```
# python3 error.py
<Response [200]>
HTTPSConnectionPool(host='www.qq.com', port=443): Max retries exceeded with url: / (Caused by SSLError(SSLError("bad handshake: Error([('SSL routines', 'ssl3_get_record', 'wrong version number')],)",),))
HTTPSConnectionPool(host='www.qq.com', port=443): Max retries exceeded with url: / (Caused by SSLError(SSLError("bad handshake: Error([('SSL routines', 'ssl3_get_record', 'wrong version number')],)",),))
HTTPSConnectionPool(host='www.qq.com', port=443): Max retries exceeded with url: / (Caused by SSLError(SSLError("bad handshake: Error([('SSL routines', 'ssl3_get_record', 'wrong version number')],)",),))
HTTPSConnectionPool(host='www.qq.com', port=443): Max retries exceeded with url: / (Caused by SSLError(SSLError("bad handshake: Error([('SSL routines', 'ssl3_get_record', 'wrong version number')],)",),))
HTTPSConnectionPool(host='www.qq.com', port=443): Max retries exceeded with url: / (Caused by SSLError(SSLError("bad handshake: Error([('SSL routines', 'ssl3_get_record', 'wrong version number')],)",),))
HTTPSConnectionPool(host='www.qq.com', port=443): Max retries exceeded with url: / (Caused by SSLError(SSLError("bad handshake: Error([('SSL routines', 'ssl3_get_record', 'wrong version number')],)",),))
HTTPSConnectionPool(host='www.qq.com', port=443): Max retries exceeded with url: / (Caused by SSLError(SSLError("bad handshake: Error([('SSL routines', 'ssl3_get_record', 'wrong version number')],)",),))
HTTPSConnectionPool(host='www.qq.com', port=443): Max retries exceeded with url: / (Caused by SSLError(SSLError("bad handshake: Error([('SSL routines', 'ssl3_get_record', 'wrong version number')],)",),))
HTTPSConnectionPool(host='www.qq.com', port=443): Max retries exceeded with url: / (Caused by SSLError(SSLError("bad handshake: Error([('SSL routines', 'ssl3_get_record', 'wrong version number')],)",),))

# python3 success.py
<Response [200]>
<Response [200]>
<Response [200]>
<Response [200]>
<Response [200]>
<Response [200]>
<Response [200]>
<Response [200]>
<Response [200]>
<Response [200]>
```

## System Information
```
1. ubuntu 18.04
2. gevent is lastest
3. request.help:
{
  "chardet": {
    "version": "3.0.4"
  },
  "cryptography": {
    "version": "2.8"
  },
  "idna": {
    "version": "2.9"
  },
  "implementation": {
    "name": "CPython",
    "version": "3.6.8"
  },
  "platform": {
    "release": "4.15.0-45-generic",
    "system": "Linux"
  },
  "pyOpenSSL": {
    "openssl_version": "1010104f",
    "version": "19.1.0"
  },
  "requests": {
    "version": "2.23.0"
  },
  "system_ssl": {
    "version": "1010100f"
  },
  "urllib3": {
    "version": "1.25.8"
  },
  "using_pyopenssl": true
}
```

## the proxy i use
```bash
wget https://github.com/snail007/goproxy/releases/download/v8.9/proxy-linux-386.tar.gz
mkdir proxy_here
tar -xzvf proxy-linux-386.tar.gz  -C proxy_here
cd proxy_here
chmod +x proxy
./proxy http -p "127.0.0.1:30000"

# you can try other parament for test:
# eg.1 daemon model
# ./proxy http -p "127.0.0.1:30000" --daemon --forever --max-conns-rate 0

# eg.2 https cert model
# proxy keygen -C proxy
# proxy http -p "127.0.0.1:30000" -C proxy.crt -K proxy.key -T tls
```
when i use eg.2:
python3 error.py
```
HTTPSConnectionPool(host='www.qq.com', port=443): Max retries exceeded with url: / (Caused by ProxyError('Cannot connect to proxy.', ConnectionResetError(104, 'Connection reset by peer')))
HTTPSConnectionPool(host='www.qq.com', port=443): Max retries exceeded with url: / (Caused by ProxyError('Cannot connect to proxy.', RemoteDisconnected('Remote end closed connection without response',)))
HTTPSConnectionPool(host='www.qq.com', port=443): Max retries exceeded with url: / (Caused by ProxyError('Cannot connect to proxy.', ConnectionResetError(104, 'Connection reset by peer')))
HTTPSConnectionPool(host='www.qq.com', port=443): Max retries exceeded with url: / (Caused by ProxyError('Cannot connect to proxy.', ConnectionResetError(104, 'Connection reset by peer')))
HTTPSConnectionPool(host='www.qq.com', port=443): Max retries exceeded with url: / (Caused by ProxyError('Cannot connect to proxy.', RemoteDisconnected('Remote end closed connection without response',)))
HTTPSConnectionPool(host='www.qq.com', port=443): Max retries exceeded with url: / (Caused by ProxyError('Cannot connect to proxy.', RemoteDisconnected('Remote end closed connection without response',)))
HTTPSConnectionPool(host='www.qq.com', port=443): Max retries exceeded with url: / (Caused by ProxyError('Cannot connect to proxy.', ConnectionResetError(104, 'Connection reset by peer')))
HTTPSConnectionPool(host='www.qq.com', port=443): Max retries exceeded with url: / (Caused by ProxyError('Cannot connect to proxy.', RemoteDisconnected('Remote end closed connection without response',)))
HTTPSConnectionPool(host='www.qq.com', port=443): Max retries exceeded with url: / (Caused by ProxyError('Cannot connect to proxy.', ConnectionResetError(104, 'Connection reset by peer')))
HTTPSConnectionPool(host='www.qq.com', port=443): Max retries exceeded with url: / (Caused by ProxyError('Cannot connect to proxy.', ConnectionResetError(104, 'Connection reset by peer')))
```

python3 success.py
```
<Response [200]>
<Response [200]>
<Response [200]>
<Response [200]>
<Response [200]>
<Response [200]>
<Response [200]>
<Response [200]>
<Response [200]>
HTTPSConnectionPool(host='www.qq.com', port=443): Max retries exceeded with url: / (Caused by SSLError(SSLError("bad handshake: Error([('SSL routines', 'ssl3_get_record', 'wrong version number')],)",),))
```

~~the reason is that proxy have almost 500 Concurrent request at that time.
so maybe proxy cannot solve too much requests at same time, i stop other program's request ,and all is fine~~

the problem not in proxy , even though 1 Concurrent request still have SSLError ssl3_get_record happend.

I solve the problem,by change this:
```
{'http': 'http://127.0.0.1:30000', 'https': 'http://127.0.0.1:30000'}
```
to
```
proxies={'http': 'http://127.0.0.1:30000'}
```
and , everything is fine.