Refactoring/subreddit input

[Jaxing]

The model takes subreddits as one hot vector instead of an index. Also handels exceptions in main and removed bias from l2.

[hsson]

The logging of error should maybe be written to a file and not just printed to the console. Any ideas on how to do this? @Mxiim ?

[hsson]

Also, this should solve issues #19 and #20

[Mxiim]

Code looks good to me.
@hsson We can create a model-specific log-file in the directory for that model, similar to the old README.txt but with logs of errors. However, the errors can be seen in tensorboard and I think we can remove the prints completely and use tensorboard. (There is also an option of downloading from tensorboard).