Transform categorical features to numerical features

MultiColumnLabelEncoder.py

## Credit to: http://stackoverflow.com/questions/24458645/label-encoding-across-multiple-columns-in-scikit-learn 

import pandas as pd
from sklearn.preprocessing import LabelEncoder

class MultiColumnLabelEncoder:
    def __init__(self,columns = None):
        self.columns = columns 

    def fit(self,X,y=None):
        return self 

    def transform(self,X):
        output = X.copy()
        if self.columns is not None:
            for col in self.columns:
                output[col] = LabelEncoder().fit_transform(output[col])
        else:
            for colname,col in output.iteritems():
                output[colname] = LabelEncoder().fit_transform(col)
        return output

    def fit_transform(self,X,y=None):
        return self.fit(X,y).transform(X)