Added Dsyr and tests
Fixed dgemv implementation
Fixed dsymv implementation and added tests
Merge pull request #35 from gonum/adddsyr

Added Dsyr and tests
merged from master
Merged from master
Merge pull request #36 from gonum/fixdgemv

Fixed dgemv implementation
Merge pull request #39 from gonum/improvedsymv

Fixed dsymv implementation and added tests
Pulled from master