Results of running SentimentAnalyzer() on Amazon Reviews Dataset.

## Background
Under Google Code-In, I used the sentiment analysis model in `TextAnalysis.jl` to analyse the [amazon reviews dataset.](https://www.kaggle.com/bittlingmayer/amazonreviews/kernels). I performed basic text pre-processing to increase the metrics of the model. Some tasks undertaken were:
- stemming words in each review
- removing corrupted characters
- removing definite and indefinite articles

I also found that `remove_numbers!()` (another pre-processing function mentioned in the Docs) gave an error on running. On further inspection, I found that it isn't still implemented in the `src/preprocessing.jl` folder. It is an issue worth looking into.

Also, a BoundsError occurred in the midst of the run.
```
BoundsError: attempt to access 32×5000 Array{Float32,2} at index [Base.Slice(Base.OneTo(32)), 5001]
```
This didn't effect the running and the results that I get are presented below.

## Result
I learnt how precision, recall and f1score are different metrics for measuring how well the model performs and was a wonderful learning experience.

**Precision :** 0.583117838593833
**Recall :** 0.5144996465068449
**F1Score :** 0.5466638895622987

### Related To:
1. #160
2. #185
3. #84

**cc** @Ayushk4 @aviks