Merge pull request #85 from SamoylovMD/master

Crout's determinant method fixed (fixes #82)
added credits for Maxim
Merge pull request #89 from SamoylovMD/master

fixes #88
added credits for Maxim
fixes #95
adds test AbtractMatrixTest.testRank_4x4_2()
fixes method AbtractMatrix.rank()
replaces invocations of set()/get() with update()
Merge pull request #97 from ewaldgrusk/fix_abstractmatrix_rank

Fixes #94
added credits for Ewald
Fixed bug in SVD (reported by Jonathan Edwards)
fixes #98
fixes #91
fixes #99
fixes #101
fixed a typo
added contributors how-to
added TODO
Refactored tests for CholeskyDecompositor. Added mock matrix class.
Refactored all decompositor's tests