Fix bug when field gets converted to blacklisted word

[a1d4r]

I found out that if a field name contains upper-case letters, then the underscore won't be appended to the resulting field name if it is reserved (blacklisted, in terms of the project). For example, one might expect ID to be converted to id_ but it appears as id in the model.

The solution is to change the order of string operations:

1. Convert unicode
2. Get rid of non-word characters
3. Make sure the field name starts with a letter
4. Convert to camel case
5. Check if the field name is blacklisted

[coveralls]

Coverage decreased (-0.06%) to 98.375% when pulling 2b7d331 on a1d4r:fix_blacklist into 62d77e6 on bogdandm:master.

[bogdandm]

Thank you, this is pretty good fix. I think there is one more minor case when after all conversions class name could shadow other global definitions in camel case (like True/False/Exception). But it could be fixed sometime in the future, it's quite rare to see field named liked this. I will look closely to this later.

[bogdandm]

Currently I could not publish new minor version because of broken/outdated Travic-CI pipeline 😞
https://travis-ci.org/github/bogdandm/json2python-models/jobs/773948039

I will migrate this project to https://www.travis-ci.com/ (or maybe github-actions) in few weeks and than I will make a new release.