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.
Shouldn't we call this "WelchT" given that that's what it is?.

Don't say "this will work", instead say what it will do. Something like:

"WelchT performs a Welch-T test which computes the probability that two datasets have identical means. The Welch-T test assumes that the data are generated ... " (etc.).

After the description of the Welch-T test, have an extra space to make a godoc line break before describing the code, as in:
// WelchT computes a Welch-T test which ...
// 
// WelchT is a function of two datasets which are represented by their mean, standard deviation, and number of samples (etc.)