Fixing stella deprecations and tutorial

[bellalongo]

Changes:
requirements.txt:

• updating packages to be compatible

download_nn_set.py:

• old code downloaded the incorrect catalog, adjusted it so it downloads the catalog from sectors 1 and 2 from Vizier

nueral_network.py:

• cleaned the lightcurve data to remove NaNs by creating a function called clean_data()
• made sure that the cadence for the input shape was an integer instead of a np.array
• created a new model using the same input layer and outputs for it to be compilable
• when compiling, adding metrics parameters and pointing the model to the compiled model
• adjusted lightcurve formatting to check if the lightcurve data is in array format or not
• reformatted the lightcurve to be of type float
• adjusted formatting for checking if the time or lightcurve are NaNs

results:

• folder to store the ensemble models

trainig_data:

• folder to store the flare catalog and the training data

tutorial.py:

• adjusted directories for downloading the data so it is accessible to all users