Code update.

1.  Modified GET_DATA_GOOGLE so that it issues a warning instead of
    throwing an error when passed a stock symbol that cannot be found on
    Google Finance, or which is listed on an unsupported exchange.
2.  Removed two test cases from TEST_GET_DATA_GOOGLE which have been made
    redundant as a result of the changes described above.
Code update.

1.  Modified GET_DATA_QUANDL so that it issues a warning instead of
    throwing an error when passed a stock symbol that cannot be found on
    Quandl, or which is listed on an unsupported exchange.
2.  Removed three test cases from TEST_GET_DATA_QUANDL which have been
    made redundant as a result of the changes described above.