Feature/issue 1087 eigen 3.2.2

#### Summary:

Update to Eigen version 3.2.2.

#### Intended Effect:

New Eigen library compatibility.  This is the version used by RcppEigen.

Made two changes in addition to swapping lib and updating makefile:

* update check_pos_definite to check for nan
* update singular value test to not use null matrix

#### How to Verify:

Run unit tests.

#### Side Effects:

Changes default matrix library.  Should not have any user-facing side effects.

#### Documentation:

None required.

#### Reviewer Suggestions:

Daniel.