Adding python 3 support

[stopic13]

Changes:

• Removed references to easy_install (deprecated) in documentation
• Removed references to python 2 in documentation
• Fixed import statements to match python 3 importing https://hackaday.com/2018/08/15/stop-using-python-2-what-you-need-to-know-about-python-3/
• Changed print statements to print() function calls
• Removed use of six library
• Renamed httplib references to http.client
• Removed reference to message attribute when catching exceptions https://www.python.org/dev/peps/pep-0352/#retracted-ideas
• Changed string concatenation to use f-strings instead of %-formattinghttps://realpython.com/python-f-strings
• Added 1.0.3 to supported versions