Merge pull request #256 from EDiLD/fix_quick

Fix quick
added callopts param to gnr_resolve and tnrs, cleaned up, closes #259
added iplant resolve fxn, closes #260
fixed namespace issues
added resolve function to unify name resolution fxns, #258
started a suite of S4 classes to define metadata for a taxon
set http = "post" for gnr_resolve queries longer than 300 records; fixes gh-262
Merge pull request #263 from dlebauer/master

set http = "post" for gnr_resolve queries longer than 300 records;
taxonclass changes
Merge branch 'master' of https://github.com/ropensci/taxize
fixed bug in col_downstream that was causing subsetting incorrectly, may help #265
added slack travis line
small fix to itisterms fxns to output NA when no data found
changed col_downstream to force use ids instead of names in while loop to avoid name collisions
added callopts param to tnrs function
updated to new roxygen2 ver, changed s3method to method in iucn_summary, added proper passing of curl options on to itis fxns
added verbose arg to man/getfullhierarchyfromtsn fxn
fixed broken tets for itis_lsid and col_downstream
put in missing verbose params in some fxns, fixed some tests, fixed unicode issue in eol_search param
fixed error in tp_synonyms addresses #274