Update vector_ar.rst

Fixing small typo in variable name, lagorder to lag_order
BLD: Don't check dependencies on egg_info for pip. Closes #1267.
Merge pull request #1381 from jseabold/fix-1267

BLD: Don't check dependencies on egg_info for pip. Closes #1267.
Merge pull request #1380 from aparij/master

DOC: Update vector_ar.rst