Add note about failed installation of PSReadLine

As raised in #18

Author: waf

README.md

@@ -8,7 +8,7 @@
 
 ## Installation
 
-There are 4 parts to configure: the colors, the powershell prompt, the cmd.exe prompt, and the titlebar color. All of these are optional.
+There are 4 parts to configure; all of them are optional:
 
 **Colors Installation**
 
@@ -25,6 +25,7 @@ For cmd.exe support, perform the same steps above but in a cmd.exe window.
     - It's currently prerelease, so you'll need to install it with `Install-Module -Name posh-git -AllowPrerelease -Force`
     - If you don't have an `-AllowPrerelease` flag, upgrade PowerShellGet with `Install-Module -Name PowerShellGet -Force` first.
 1. Ensure the latest version of PSReadLine (2.0 or later) is installed. It's installed by default in Windows 10, but you'll most likely [need to upgrade it](https://github.com/lzybkr/PSReadLine#user-content-upgrading).
+    - You can verify that 2.0 was installed by running `(Get-Module PSReadLine).Version`. If the installation does not appear to work, please see [this issue in PSReadLine](https://github.com/PowerShell/PowerShellGet/issues/318#issuecomment-418605987)
 1. Include [this powershell configuration](https://github.com/dracula/powershell/blob/master/theme/dracula-prompt-configuration.ps1) in your PowerShell `$profile` file.<sup>[1](#whats-the-powershell-profile-file "What's the PowerShell `$profile` file?")</sup>
 
 **cmd.exe prompt**