<!--- Provide a general summary of your changes in the Title -->

## Description
<!--- Use this section to describe your changes and how they're affecting the code. -->
<!-- If your changes required testing, include information about the testing environment and the tests you ran. -->
Added alpha support for Norwegian bokmål.

## Types of changes
<!--- What types of changes does your code introduce? Put an `x` in all applicable boxes.: -->
- [ ] **Bug fix** (non-breaking change fixing an issue)
- [x] **New feature** (non-breaking change adding functionality to spaCy)
- [ ] **Breaking change** (fix or feature causing change to spaCy's existing functionality)
- [ ] **Documentation** (addition to documentation of spaCy)

## Checklist:
<!--- Go over all the following points, and put an `x` in all applicable boxes.: -->
- [ ] My change requires a change to spaCy's documentation.
- [ ] I have updated the documentation accordingly.
- [x] I have added tests to cover my changes.
- [x] All new and existing tests passed.