fixes for weighted kernel fits
bug fixes
adding tests
BUG: kde normalize weights, adjust tests (use evaluate)
BUG kernels.CustomKernel missing asarray, add unittest (only Gauss passes)
TST: add test kde with weights, only Gaussian kernel
BUG: fix bounded support kde, divide by total nobs, enable test
TST: add tests for KDEUnivariate with weights, Cosine fails, some not available
ENH: add Cosine2 kernel, same cosine kernel as Stata closes #1245
ENH: kernels add _kernel_var(not used yet)
ENH add density var and conf_int to kernels, regression tests only
REF/TST: test for kernel constants
DOC kde with confint add example script
DOC/STY rename inDomain -> in_domain, small docstring improvement
Merge pull request #1240 from josef-pkt/kde_weights_1103_823

Kde weights closes #1103 closes #823 closes #1245