Merge pull request #1 from jschwab/master

fix bug in profile_data by when specifying profile_number
Clean up comments and make sure all lines are no longer than 80 characters to
aid in readability. Add option to not clean out backups in MESAData files by
setting the optional second parameter to false in the constructor. Also by
default, the history cleanup, if performed, will not output the number of lines
removed. This can be undone by setting the third parameter (also optional) to
true.
Remove offending Dir.exist? command that is uncompatible with older versions
of Ruby.
Replace all for loops with more ruby-like iterators.
Make all MESAProfileIndex methods accessible from MESALogDir. No longer need to
access the MESAProfileIndex object via #profiles, but it is left in for
backwards compatibility. Also alias history_data to history.
Remove all "setter" methods for MESALogDir since they essentially did nothing.
Add warnings when data or header calls have no column/field to query. Fix bug
where giving a float to profile_with_model_number would give no result. Big update to the README to include/exclude the proper methods added/removed in the
last few commits.