Added init__ file for newton_polynomials
Added DegreeIndexing indexing type
EuclideanBall and Gegenbauer weight function
XuBallBasis (2D) evaluation seems to work
Some new polynomial bases

- Laguerre polynomials
- Support for discrete measures in OrthogonalPolynomialBasis
- Discrete Chebyshev polynomials
- 2D XuBallBasis bug fix
Proper recurrence form for GeneralizedGegenbauerPolynomials
Updated least interpolation for submission to DB
Removed 'quad' package
Fixed Interval1D calling syntax
Oops, forgot to add TensorProductBasis.weight