Added functionality to allow x-coordinates to be categorical data, rather than just numeric data, will plot y-coordinates equally spaced in order that they are input, with x-coordinates as the labels.  Also allows user to control plot width and height, and defaults to use the whole width of the existing terminal as the width, and use half of the height.
Make Rio work on Mac
Two changes: 1: added triple backslash-n for newline in cat statement in callR function for escaping newline in bash script, otherwise did not work on bash in my mac.  Please test to see if it works for other bash as well, but it should.  2: Changed creation of OUT and ERR tempfiles.  As currently made, would create a file, and then append either .png or .err to the FILENAME in the bash script, and then would write to the filesnames with the new suffixes.  But the mktemp command makes the un-suffixed files as well, and they never get cleaned up in the temp directory.  Appending the .png and .err suffix in the inner mktemp command call fixes that (again, tested on a Mac).
Two changes: 1: Use triple-backslash-n in the cat call in callR function.  Original formulation, with one-backslash-n in the call was causing an error, because I believe that bash was interpolating this to an actual newline in the code, not the backslash-n sequence to pass to Rscript.  Should be tested on Linux, but works on Mac.  2: Creation of temp files left two empty files, one with name of OUT but without the .png suffix, and one with the name of ERR but without the .err suffix.  Added call in trap call to clean up those files, as I cannot figure out a portable way to just create single temp files with .png and .err suffix, as the --suffix arg to mktemp is not universal.
Merge pull request #18 from mpettis/Rio-mac

Rio mac