DOC: update DF.as_matrix and DF.values.  Closes gh7413
Merge pull request #7417 from clham/7413

DOC: update df.as_matrix and df.values.  Closes gh7413
FIX integer column names for older sqlalchemy version GH6340, GH7330
Merge pull request #7456 from jorisvandenbossche/sql-fix7330

FIX integer column names for older sqlalchemy version GH6340, GH7330
BUG/CLN: LinePlot uses incorrect xlim when secondary_y=True