hyQSAR: Hybrid QSAR model

This function create a training-test split of the dataset

1	training_test_split(X, y, p_train)

`X`	is the matrix of the dataset with samples on the rows and features on the column
`y`	is the reponse vector of the training set
`p_train`	is the percentage of samples to be used in the training set

a list with the following components:

`X_train`	a matrix with the training samples
`X_test`	a matrix with the test samples
`y_train`	the numeric vector of responses for the training samples
`y_test`	the numeric vector of responses for the test samples