ck_cohort_rw: Initial implementation with validation test.

I still need to implement benchmark tests and write documentation.  The reader-writer cohort locks also required that I add a method to the existing ck_cohort framework to determine whether or not a cohort lock is currently in a locked state.
ck_cohort_rw: Cleaned up regression files from last commit
ck_cohort_rw: Added latency and throughput benchmark regression tests
ck_cohort: Fixed regression tests based on ck_cohort_rw changes
ck_cohort: Updated documentation to reflect ck_cohort_rw changes
ck_cohort_rw: Reduced line wrapping
ck_cohort_rw: Removed unused member variable
ck_rw_cohort: renamed ck_rw_cohort namespace
ck_rw_cohort: Removed backwards jump
ck_rw_cohort: Added read-preference logic and updated validation test to use it
ck_rw_cohort: Added neutral reader-writer lock
ck_rw_cohort: Added benchmark tests for reader-writer cohort locks
merged from upstream repo
ck_rwcohort: Renamed ck_rwcohort namespace
Merge branch 'master' of https://github.com/sbahra/ck
ck_rwcohort: Updated .gitignore to reflect new ck_rwcohort naming
ck_rwcohort: Fixed indentation and looping logic and added initial documentation
ck_rwcohort: Fixed Makefile for automated regression testing
Merge branch 'master' of https://github.com/sbahra/ck
Merge branch 'master' of https://github.com/bscheinman/ck