Update README.md

Fixed typo in link to wiki. Used to point to rackspace user instead of rackerlabs.
D-12493: return 409 instead of 400 when entryId is not unique
Merge pull request #242 from mark-donoghue/master

Fixed typo in README file
D-12493: catch exception thrown when unique constraint is violated and return 409
D-12493: add more coverage in integration tests
Changing connection pooling to tomcat
D-11097: Adding content-type to error messages
D-11097: Adding content-type to error messages
Merge pull request #244 from mattkovacs/master

B-49312: Use Tomcat's Connection Pool
Merge pull request #243 from shintasmith/D-12493

return 409 instead of 400 when entryId is not unique
Fixing merge conflicts
Merge pull request #246 from mattkovacs/D-11097

D-11097: Adding content-type to error messages