Localflavor Nepal: Support for nepal added in django-localflavor

[vishalpandeynits]

Support for Nepal Added as requested by this issue #414

What Fields are added ?

• [x] Field for zones of Nepal.
• [x] Field for provinces of Nepal.
• [x] Field for districts of Nepal.
• [x] Field for Postal Code of Nepal.

All Changes

• [x] Add an entry to the docs/changelog.rst describing the change.

• [x] Add an entry for your name in the docs/authors.rst file if it's not already there.

New Fields Only

• [x] Prefix the country code to all fields.

• [x] Field names should be easily understood by developers from the target localflavor country. This means that English translations are usually not the best name unless it's for something standard like postal code, tax / VAT ID etc.

• [x] Prefer 'PostalCodeField' for postal codes as it's international English; ZipCode is a term specific to the United States postal system.

• [x] Add meaningful tests. 100% test coverage is not required but all validation edge cases should be covered.

• [x] Add .. versionadded:: <next-version> comment markers to new localflavors.

• [x] Add documentation for all fields.

[benkonrath]

I'll be a able to take a look at this next week. Thanks for the PR!

[benkonrath]

I've recently fixed the CI so we have testing on PRs again. Could you rebase this PR on the master branch which will run CI? The tests will probably show you some formatting/linting problems that will need to be fixed. I'm back online regularly so I'll be able to look that this as soon as the tests pass. Thanks.

[vishalpandeynits]

@benkonrath I have made the necessary changes, please check once and let me know if any other changes are required.

[benkonrath]

Thanks!