TST: add bounds-checking preamble to groupby_X cython code
ENH: add bounds-checking preamble to groupby_X cython code
TST: Enforce grouper=f() result has len(labels) == len(data) GH3035
BUG: Enforce grouper=f() result has len(labels) == len(data) GH3035
DOC: Update v0.11.0.txt