allows extraction in grams and adds a test accordingly.
edits the extract_in_grams test for readability
edits the extract_in_grams test for readability
adds isovector comparison tests, these fail as @gidden predicted, explaining a lot of drama I was seeing in actual simulations.
this fixes all compiler-related errors for me, iso vectors still don't equate to equal
added an isovector test to confirm the == operator works as intended
added simple test to diagnose the problem
changed from testing equality of pointers to equality of underlying compositions
added isotopic checks to other absorb tests just in case
Merge pull request #476 from katyhuff/extract_eps

Allows Material::extract to optionally occur in grams, fixes compiler related issues with the material class, and updates the equality for isovectors. Previously, isovectors compared equality based on pointers, now they compare based on equality of their compositions. It is not clear to me how this will affect performance; however, I believe this is the correct behavior for the == operator. If we really need to check comp map pointer equality, we can add a different method to do that.