DataFrame<T>.append(vararg values: Any?) does not fail on incorrect arguments passed

[sulevsky]

If an invalid number of arguments are passed to DataFrame.append then the assertion is not checked (by default is turned off) and unchanged DataFrame is returned (which is a bit misguiding)

1. Create a DataFrame with 2 columns
2. Call append with a single parameter

Ex.

 dataFrameOf("name", "age")(
        "Alice", 15,
        "Bob", 20)
        .append("John")

Expected: exception or updated DataFrame

[koperagen]

Hi! Thank you for the report and pointing that 'assert' is turned off by default.

[koperagen]

Hi! It should now throw an exception on `0.9.0-dev-1079