Add checkbox and select for summarization
Initial search controller logic for summarizing

rows are annotated with the taxon id corresponding to the selected
summarization level.  Then, if summarization was enabled, the rows are
chunked by this id.

Currently, the summarization only selects the first otu in the list -
it does not actually combine the traits/metadata.  But it does reduce
the number of results.
Summarization is functioning but not perfect yet.

Changed summary_taxon_id to summary_taxon in row_hashes
Uses deep_merge to summarize but this may require rails 4.0.2
merge trait hashes in array method, add a test case for averaging
implemented summarization/tests for continuous traits
Add extra trait for summarization test
Avoid nil access if no merged valye
Use merge_trait_hashes in results

Working for continuous traits
Improved merge, add :collect
Use merge_trait_hashes in categorical traits
Use category_id to link codings to sources
Merge pull request #162 from NESCent/summarize_results

Summarize results