Adding another reference.

Signed-off-by: Eduardo Tenorio <embatbr@gmail.com>
Updating tests for features/

Signed-off-by: Eduardo Tenorio <embatbr@gmail.com>
Updating docs.

Signed-off-by: Eduardo Tenorio <embatbr@gmail.com>
Calculating the Delta and Delta-Delta from MFCCs.

Signed-off-by: Eduardo Tenorio <embatbr@gmail.com>