Adjust weighted completeness metric

After refactoring the completeness metric, I have made adjustments to
the weighted completeness metric. I provided its own method to count
the maximum number of fields, changed the count in properties method
as well as the constructor.

I probably should extract some of the redundant code into a separate
method.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Added the field initializer again

I half-accidentally removed the field initializer for the count fields
method. This time I do not use a method parameter with default value,
but a simple statement.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Make some controller more robust

I have added some exception handling to the controller. This way the
application does not crash when the database has no repository data
yet.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Add Travis CI configuration file

I have added a .travis.yml for trying to set up continuous integration
with Travis CI for this project once again.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>