Improves dateutil parsing

Closes #133
Fixes #183, #185, #228
Introduces `-on` option

Fixes #246
Tests for date parsing and `-on`
Version bump
Fix bug when omitting day in parsing
Conditional dateutil for python 3
Merge pull request #247 from maebert/1-9-0

Greatly improved date parsing
Docs update

Closes #176
Don't correct future timestamps if year is present in input
Regression test for future timestamps
Version bump
Merge pull request #248 from maebert/1-9-1

Fix parsing of  future timestmpas
Merge pull request #1 from maebert/master

Merging commits from maebert