Merge pull request #16 from mcbrandt13/feature

singular_node method added, and test.
Merge branch 'master' of github.com:PLOS-Web/xmlgroomer
Merops-only grooms removed
Merops-only groom tests removed
Merge pull request #17 from mcbrandt13/unmerops

Unmerops
Merge branch 'unmerops'
Merge branch 'master' of github.com:PLOS-Web/xmlgroomer