Update README.md documentation
Update README.md documentation

Added:
    - Added new key features supported.
    - New test directory section entry for RAS.

Change-Id: I15c68507493be63ef88a986b9adff3bcd857b20b
Signed-off-by: George Keishing <bef0a9ecac45fb57611777c8270153994e13fd2e@in.ibm.com>

openbmc/openbmc-test-automation,openbmc/openbmc-test-automation