implement additional tests for groupby apply methods
simplify groupby's std method
add sem to nanops and pandas object apply methods
Merge pull request #7133 from toddrjen/sem

ENH: Implement "standard error of the mean"
BUG: Bug in .loc with a list of indexers on a single-multi index level (that is not nested) (GH7349)
Merge pull request #7350 from jreback/mi_index

BUG: Bug in .loc with a list of indexers on a single-multi index level (that is not nested) GH7349
DOC: minor v0.14.1 editing