Add 3 new unit tests for arima_process: arma_acovf, arma_acf, arma_generate_sample
TST: AR predict one more test adjustment to allclose
BUG: sandwich_covariance: fix typo, add simple test, closes #980
REF/TST stats.proportions use warning, catch in test (removes test noise)
Merge pull request #982 from josef-pkt/misc_fixes_11

Misc fixes 11
COMPAT: Pandas 0.8.1 compatibility. Closes #983.
Merge pull request #984 from jseabold/fix-983

COMPAT: Pandas 0.8.1 compatibility. Closes #983.
ENH: Prefer to_offset to get_offset. Closes #964.
STY: Remove unused exception catch.
Merge pull request #986 from jseabold/use-to-offset

ENH: Prefer to_offset to get_offset. Closes #964.
MAINT: Print versions script/function
MAINT: Add executable file permissions.
MAINT: Add developer tool versions.
ENH: Try to find out installed statsmodels version.
ENH: Import show_versions into api.
ENH: Add file path to versions script.
Merge pull request #985 from jseabold/version-script

MAINT: Print versions script.
TST: AR dynamic_predict adjust test precision again, see #910
TST: power lower precision for normal_power closes #991
Merge pull request #992 from josef-pkt/misc_fixes_12

Misc fixes 12: adjustments to unit test