Merge pull request #14 from Chaircrusher/DefaultOrigin

BUG: if origin isn't set in nrrd reader, set it to a reasonable default
Merge pull request #15 from Chaircrusher/FixSlicerExtensionBuild

COMP: Check for UKFTractography_BUILD_SLICER_EXTENSION
STYLE: Remove outdated documentation.
ENH: Use Better tolerance for different slightly differnt results

Allow for upto a 10th of a point difference.
BUG: A new baseline image is needed.
ENH: use the Eigen template library for linear algebra operations

COMP: fix minor compile warnings
ENH: Changes verified to pass all tests.
PERF: Avoid unnecessary matrix copies by using const references.
PERF: Move initialization of diagonal to class

The diagonal matrix could be initialized 1 time and used
many times by moving initializing it in the constructor.

Also converted from struct to class and add Eigen memory
alignment.
ENH: Provide more robust testing.  False positives were reported when zero fibers were found.
COMP: remove output files before running tests
COMP: clean up QuadProg++_vnl.cc
PERF: Refactoring again to minimize memory copies.

Continue to push variables to be local and remove
unnecessary intermediate variables. Also use const
reference pointers where possible to avoid unncessary
copying of memory.
PERF: Replace LU with Eigen equivalent

This is the first test at repalcing matrix
solution with Eigen equivalent version.
PERF: Ensure that the FilterModel used for initialization never changes.
COMP: intermediate changes to get rid of vnl_vector_ref
ENH: Conversion to Eigen continuation.
ENH: Update QuadProg to use Eigen classes.
PERF: Replace vnl with Eigen cholesky decomposition.
PERF: Provide custom allocation to ensure alignment

As documented on http://eigen.tuxfamily.org/dox-devel/group__TopicStlContainers.html

special care needs to be taken to ensure alignment in Eigen.