Update Gamgee readmee to remove boost build and add cmake.
Merge pull request #392 from broadinstitute/ldg_updateReadme

Update Gamgee readmee to remove boost build and add cmake.
Add a method to help with filter/field iteration
- Add explanatory comments
Merge pull request #393 from broadinstitute/jt_max_field

Add a method to help with filter/field iteration
Check for missing variant in MultipleVariantIterator - important if one
of the inputs is a blank VCF

Added a simple test case for empty VCF traversal using MultipleVariantIterator