Added note to increase open file limit on Linux (#936)

Signed-off-by: Adrian Sutton <adrian.sutton@consensys.net>

docs/Installation/Build-From-Source.md

@@ -58,6 +58,10 @@ $ cd pantheon-<version>/
 $ bin/pantheon --help
 ````
 
+!!! note "Linux Open File Limit"
+    If synchronizing to MainNet on Linux  or other chains with large data requirements, increase the maximum number 
+    of open files allowed using `ulimit`. If the open files limit is not high enough, a `Too many open files` RocksDB exception occurs. 
+
 Continue with the [Private Network Quickstart](../Tutorials/Private-Network-Quickstart.md) or [Starting Pantheon](../Getting-Started/Starting-Pantheon.md).
 
 

docs/Installation/Install-Binaries.md

@@ -51,6 +51,10 @@ pantheon --help
     Pantheon requires Java 8+ to compile; earlier versions are not supported.
     Pantheon is currently supported only on 64-bit versions of Windows, and requires a 64-bit version of JDK/JRE. 
     We recommend that you also remove any 32-bit JDK/JRE installations.
+    
+!!! note "Linux Open File Limit"
+    If synchronizing to MainNet on Linux or other chains with large data requirements, increase the maximum 
+    number of open files allowed using `ulimit`. If the open files limit is not high enough, a `Too many open files` RocksDB exception occurs. 
 
 ### Install from Packaged Binaries