Fix a size comparison

To correctly compare two sizes, each specified using a number with a letter suffix (M, G, &c), you have to multiply each number by the factor implied by the suffix, not divide it.  The current code would accept a change from e.g. 1G to 1M as an increase.
Merge pull request #58 from tih/patch-1

Fix a size comparison
Merge pull request #3 from puppetlabs/master

Upstream pull