Update Howto and setup.py about x11_hash package required for Dash

docs/HOWTO.rst

@@ -14,7 +14,8 @@ small - patches welcome.
 + irc:      Python IRC package.  Only required if you enable IRC; ElectrumX
             will happily serve clients that try to connect directly.
             I use 15.0.4 but older versions likely are fine.
-
++ x11_hash: Python X11 Hash package. Only required if you use ElectrumX
+            with Dash Network (Both Mainnet and Testnet). Version == 1.4 ;
 
 While not requirements for running ElectrumX, it is intended to be run
 with supervisor software such as Daniel Bernstein's daemontools,

setup.py

@@ -9,6 +9,7 @@ setuptools.setup(
     python_requires='>=3.5',
     # "irc" package is only required if IRC connectivity is enabled
     # via environment variables, in which case I've tested with 15.0.4
+    # "x11_hash" package (1.4) is required to sync DASH network.
     install_requires=['plyvel', 'aiohttp >= 1'],
     packages=setuptools.find_packages(),
     description='ElectrumX Server',