Fix automated NPM deployment process (applegrew#505)

Use skip_cleanup to distribute build artifacts.

Fix travis config (applegrew#504)

Add Python 3.7 support (applegrew#502)

Fix applegrew#493 -- Fix Python 3.5 compatibility

Ref 1954bf5

Update Select2 library to version 4.0.5

Add option to exclude the Select2 library from form media (applegrew#484

)

Fallback i18n js files for zh-hans/zh-hant. (applegrew#468)

* Fallback i18n js files for zh-hans/zh-hant.

* Use Django admin's built-in SELECT2_TRANSLATIONS to determine the lang of i18n js files.

Fix applegrew#461 -- Remove explicit Django version classifiers

Fix applegrew#451 -- Remove none ASCII char