incorrect observations in README.md

[conradsnicta]

In the Observations section of README.md, it is stated that:

As expected Armadillo with internal BLAS/LAPACK wrappers performance is pretty poor.

This is incorrect, as the meaning of the "internal wrapper" is wrong. There is either a wrapper for an external library, or there isn't. A re-implementation of a function is not an "internal" wrapper, but simply internal functionality. The correct wording for the quoted problematic statement should be:

Armadillo without the use of OpenBLAS or MKL wrappers obtains poor performance. However, when the wrappers for OpenBLAS or MKL are enabled within Armadillo, the performance is virtually the same as for the other libraries.

[olmallet81]

Hello, you are right indeed, I will modify, thanks for noticing me and for your great work on Armadillo.