pip 19+ is now needed to install bigchaindb (#2645)

Signed-off-by: Troy McConaghy <troy@bigchaindb.com>

docs/server/source/simple-deployment-template/set-up-node-software.md

@@ -13,6 +13,7 @@ MongoDB and Tendermint.
 ## Install BigchainDB Server
 
 BigchainDB Server requires **Python 3.6+**, so make sure your system has it.
+
 Install the required OS-level packages:
 
 ```
@@ -21,6 +22,12 @@ sudo apt install -y python3-pip libssl-dev
 # Ubuntu 16.04, and other Linux distros, may require other packages or more packages
 ```
 
+BigchainDB Server requires [gevent](http://www.gevent.org/), and to install gevent, you must use pip 19 or later (as of 2019, because gevent now uses manylinux2010 wheels). Upgrade pip to the latest version:
+
+```
+sudo pip3 install -U pip
+```
+
 Now install the latest version of BigchainDB Server.
 You can find the latest version by going
 to the [BigchainDB project release history page on PyPI](https://pypi.org/project/BigchainDB/#history).