added an equivalecny to convert between kelvin and eV
added tests and doc
changed tests(removed magic number),removes scipy import
added doc for the temperature_energy equivalencies
removed uncessary import
changed example
updated CHANGES.rst about the temperature-equivalencies feature
corrected simple typing mistake
added keyword for better understanding
changed the doc
Merge pull request #2637 from kaichogami/keV_kel

kelvin to eV