Allowing value transform functions, multiple data sets, missing values, etc.

Also, pulling in a gemspec file, because bundler was bitchy.
Cleaning up boundary calculations, so the graph actually fits in the area desginated.
Autoscaling on the y axis
Time-aware horizontal scaling
Deal with the problem when max and min are the same thing
Moving the left axis in if the values are big
Deal with graphs where there is only one point along the x axis
Horizontal graphing capability
labeling bars in a bar grpah
Fixing bar alignments
Fixing bar graphs with ignore_set_spacing
Fixing bar graphs with ignore_set_spacing
Fixing bar graphs with ignore_set_spacing

Yes, this is easier than rebundling to path again
Zip only runs to the length of the first array, my bad. So, sort the arrays by length first
Merging tithonium's updates.
Updated version number.
Updated version in gem spec.
dealing with @valueAxis is nil
Merge branch 'master' of https://github.com/erich/prawn-graph