Enable authentification via argurments

[TeddyCr]

Description

Current authentification to the Twitter API is managed through environment variables. To extend usability, we need to enable authentication with arguments passed to the API() class

Scenario

Example of authentification using arguments:
connection = twitterSentiment.API(client_key=KEY, client_secret=SECRET)

Files

Current authentification method can be found here

Tasks

• Update API() class to add authentification via arguments
• Develop test to ensure existing authentification is not broken (after update)