starting to add tests via testthat + refactoring

need to get vds wim pairs from couchdb, so refactoring a bit and taking
the opportunity to add proper test of the new, more modular functions
that I am writing

modified:   lib/get_couch.R
new file:   lib/paired.Rdata.R
modified:   lib/wim.loading.functions.R
new file:   test/test_get_couch.R
new file:   test/test_paired_Rdata.R
Merge branch 'master' of https://github.com/jmarca/calvad_rscripts