Improve installer and bug fixes

Changed

• Improve setup.py build script generating pickled files when build bdist.
• Use pytest and pytest-cov for unittest.
• Use tox for CI/CD in travis-CI and appveyor.

Fixed

• Kanwadict: remove entry for 市立 as ichiritsu
• Issue #59: fix 0x30f7-30fc katakana convertion to be as same as in Hiragana.
• Appveyor: twine upload credential environment variable name.

Deprecated

• Drop python2.6 and python 3.3 from test target.