Upgrade rasa nlu

[ErickKramer]

Is your feature request related to a problem? Please describe.

• Recently, rasa got a major upgrade and merged rasa_core and rasa_nlu into a single library called rasa.

• Models trained in the new version of rasa (1.1.5) cannot be loaded into the older version of rasa currently install in lucy (rasa_nlu 0.14.0).

• New version of rasa does not support python 2.7 mentioned here.

• Way of generating nlu models changed, but we have created already a repository overcoming this problem, temporarily in here.

Describe the solution you'd like

• Install the new version of rasa (1.1.5), as it might have better nlu models that could improve performance.

• This would require using python3 instead of python 2.

Additional context

• The major concern is whether rasa is going to be able to be used with our current nodes in ROS if we upgrade.

• An alternative is to use an older version of rasa for both training and deployment so that python 2 is still supported.

[argenos]

This is related to #175 and #176

@PatrickNa @alex-mitrevski who is taking care of creating the script to test python3 with kinetic? I believe in #175 no one volunteered.