Check for nil instead of falsiness

This allows required boolean fields to be set to false.
Add test case for required booleans

This exercises a required boolean field set to false
Refer to records' factory functions
Merge pull request #1 from bts/fix-false-required-booleans

fix exception when setting non-optional bool field to 'false' (pull request #1)
Merge pull request #2 from bts/record-factory-fns

refer to records' factory functions '->Type' and 'map->Type'
Release 0.1.2
Update README.md
Upgraded Dependencies.
Merge branch 'master' of https://github.com/xsc/thrift-clj