gesdd, major refactoring of math headers, moved #factorize_lu to Ruby
source from C++.
Added gesdd specs
Updated history
Added NMatrix#gesdd and NMatrix#gesvd
Added #supershape for shape of slice parent
Updated N[] shortcut to NMatrix[]

Following John Prince's suggestion, I modified the N[] shortcut to use
NMatrix[] instead.

close 118
Updated spec for inline constructor
Updated other specs with NMatrix[]

Ops, almost forgot them.
Re-added N[] shortcut as an alias to NMatrix[]
Merge pull request #119 from agarie/update-shortcut

Aliased N[] shortcut to NMatrix[]
Update history
Updated [] operator so a matrix behaves like a vector when a shape
component is set to 1.
Disallowed API creation of NVector
Eliminated NVector and allowed NVector-like slicing in NMatrix.
Update history
Attempt at fixing pretty_print, doesn't work great for dim > 3
Slight improvement in pretty_print
Rudimentary pretty_print for 3d matrices
Fixed #120
Lined up columns in pretty_print