Adding Eigen library headers
Adding faster functions for matrix computation
Adding ISpreadRank functions using Eigen objects
Removing old ISpreadRank functions
Last modifications
Merging master
Fixing problems according to Paul's remarks
Fixing build and tests (removing the collision-prone U macro).
Merge pull request #31 from PaulDib/SpeedingUpISpreadRank

Speeding up IspreadRank