implement norm (#14)
integral --> sum (#13)

following the same logic as chebfun, and bumpy, the integral is now called 'sum'
allow initialisation with integer values
allow initialisation with a list of chebcoeffs
fixup to 00d7a4b048 (chebfun works for scalar and tensors)
exp and cos ufuncs added (#13)
chebpoly -> basis

chebpoly is supposed to compute the Chebyshev expansion of a function
move dichotomy method to an independent function
misplaced encoding instruction
do not store Chebyshev coefficients

it is the same as the Matlab implementation: just store the interpolation values at Chebyshev points
move differentiator function to the end
more sensible names for points and values attributes
do not store interpolation points
repr is now unambiguous

in principle, the return value of repr suffices to create a new instance of Chebfun
implement higher order differentiation
rename idct -> chebpolyval
more consistent call to interpolation_points
clearer interface to function interpolation_points

it returns N points instead of N+1
big change in Chebfun initialisation

the Chebfun constructor is now dead simple: it only accept an array of interpolation values over Chebyshev points

Chebfun also has class methods for initialisation when the type is known, for instance Chebfun.from_function, or Chebfun.from_chebcoeff.

The new "smart" constructor is now the *function* "chebfun", which guesses the right initialisation class method to call.
fix initialisation from vector functions

factor out common functions for the tests