Students T-Test

Added functions for Students T-Test one sample and independant sets and a function to convert a t-value to a p-value. Not sure about the naming, if you would like me to change the function names and resubmit requrest, let me know. I have tests, I will add examples next week and I would like to add dependant sets after that.
For future reference, all functions in this package (where it's appropriate to do so) support weighted samples.
However, in this case, this function should just take in the means and standard deviations directly (like the other functions in the package). This will require an additional number of samples parameter. This will also need documentation.