BUG: sparse: fix bugs in dia_matrix.setdiag

- hide details of the internal dia_matrix data representation in
  setdiag(), so that behavior matches the other spmatrix types

- fix bugs in resizing self.data, which doesn't always have
  self.shape[1]==N

- add scalar broadcasting behavior to setdiag() for all matrix types
BUG: sparse/dsolve: detect invalid LAPACK parameters in superlu and bail out gracefully
MAINT: add pyflakes to Travis
MAINT: initialize variables to make pyflakes happy

The variables will receive their values during the running of the value.
BUG: fix missing imports etc typos found by pyflakes
BUG: io/arff: remove dead code

The `types` and `r_mend` variables are undefined, making the routines
tokenize_multilines and floupi inoperable.
BUG: sparse/bicgstab: remove call to undefined routine

There's no routine get_psolve. Just assume psolve is given.
MAINT: weave: dead code removal in benchmark
MAINT: clean up list comprehension redefining variables

Not bugs per se here, but let's make pyflakes happier.
Merge pull request #3384 from pv/travis-pyflakes

MAINT: add pyflakes to Travis-CI
BUG: stable evaluation of expit
TST: do not use yield test within TestCase subclass
TST: use assert_allclose with tiny abs tolerance for expit test
TST: more expit tests
TST: actually use the dtype
Merge pull request #3386 from argriffing/expit-evaluation

BUG: special: fix stable evaluation of expit
BUG: SuperLU: fix missing declaration of dlamch

SuperLU 4.3 called some functions returning floats without declaring
them. On i386@linux call convention, this fails to clear floating point
registers after call. As a result, NaN can appear in the next floating
point operation made.
BUG: sparse: downcast 64-bit indices safely to intp when required

Downcast 64-bit indices to 32-bit intp when required, but check
whether this is a safe operation, to be sure.

ufunc.reduceat and np.bincount deal only with intp data type.
BUG: nonlinear solvers are not confused by lucky guess
TST: sparse: silence some deprecationwarnings

The code triggers these only on Numpy < 1.9