Merge pull request #32 from DanGrayson/linalg

Linalg
Fixed bug in Divisor.m2 tests: minimalPrimes ideal 1_R crashes

Fixed topCoefficients, there were at least two bugs present, one causing
that crash.  They are now fixed.
merge m2/master into linalg
increase version number to 1.6.1

The linalg branch of Mike's has just been merged, and the
tests all pass.
increase version number to 1.6.1.1

We tagged the previous commit with "version-1.6.1", to
indicate that it's relatively stable.