lrdp-v2: README: document Python 2.7 requirement

The parser now requires Python 2.7 so that 2.7-specific features can be
leveraged. Update the README to reflect this.

Change-Id: I7e1ba9f99f077c7f48ed7b44ab24f56f0f18c3ea

linux-ramdump-parser-v2/README

@@ -43,6 +43,12 @@ linux-parser-output.txt is used
 The list of features parsed is constantly growing. Please use --help option
 to see the full list of features that can be parsed.
 
+System requirements
+-------------------------------
+Python 2.7 is required to run this tool. It can be downloaded and
+installed from https://www.python.org/ or through your system's
+software package manager.
+
 Setting up the toolchains
 -------------------------------
 The parser relies on having access to gdb and nm to work. You will need to