Simple temperature converter tool

1. Can convert from Celsius to Fahrenheit or Fahrenheit to Celsius

1. Rejects temperature values that would be below Absolute Zero

1. Bump version number - forgot this in v2.0.

1. Add MIT License.

1. Add License summary to source code files.

Copyright (c) 2017 Matthew Wright. Licensed under MIT License. See LICENSE.txt for further details.

This software should be distributed with a LICENSE.TXT file in the solution root. Alternatively you can find a copy of the license in the github repository: https://github.com/wiganlatics/temperature-converter. The MIT License text is also available at: https://choosealicense.com/licenses/mit/.