Updated Matlab Lesson one as per recommendations

-data renamed earlier
-polyval function used instead of referencing by coefficients
-more description about histogram
-generally more explicit in description, mentions help and doc functions
as well as (good) documentation on mathworks site.
-mean, median, and standard deviation provided as problems to "match
values" for
-challenges students to change format of plots using documentation on
the plot function.
-Matlab indexing clarified, RC mnemonic introduced to help remember
-plots now have labels and titles