Merge pull request #7 from OuhscBbmc/dev

Incorporates & documents new parameters added by @rparrish (Fixes #3, #5, #6)
Added some TODOs and updated NEWS.
Added `redcap_read_batch()`
batch reading: Orders the IDs after initial query.
Removing ggplot2 from suggested packages
Added some references in the documentation
Updated SSL Certs With Dec 2013 Version

From http://curl.haxx.se/ca/cacert.pem
Updating error messages in tests

The returned API error message changed slightly.  Also about to add to
R-Forge.
Added link to R-Forge on README.md
Merge pull request #16 from OuhscBbmc/RefClassTry

Updating Certs & adding R-Forge link
renaming `df` parameter to `d`
added 'column sanitize'
Merge pull request #17 from OuhscBbmc/RefClassTry

Ref class try
renaming `redcap_read` to `redcap_read_oneshot`
Renamed `redcap_read_batch`  to `redcap_read`; added tests
Merge pull request #18 from OuhscBbmc/RefClassTry

renaming `redcap_read()`
documented `create_batch_glossary()` and made it public
renaming `redcap_write` to `redcap_write_oneshot`
Added internal `redcap_write` as batch
updating packages necessary for development