removing PATH setting.

"psql" may not exist in /usr/bin and /bin.
updating README.
Add document of schema driver interface via HDBC.
Rename local variable.
Merge pull request.
Update readme.
Renamed.

--HG--
rename : relational-join-HDBC-pgTest/sample/1/Group.hs => relational-join-HDBC-pgTest/example/1/Group.hs
rename : relational-join-HDBC-pgTest/sample/1/Membership.hs => relational-join-HDBC-pgTest/example/1/Membership.hs
rename : relational-join-HDBC-pgTest/sample/1/README => relational-join-HDBC-pgTest/example/1/README
rename : relational-join-HDBC-pgTest/sample/1/User.hs => relational-join-HDBC-pgTest/example/1/User.hs
rename : relational-join-HDBC-pgTest/sample/1/create.sh => relational-join-HDBC-pgTest/example/1/create.sh
rename : relational-join-HDBC-pgTest/sample/1/drop.sh => relational-join-HDBC-pgTest/example/1/drop.sh
rename : relational-join-HDBC-pgTest/sample/1/querySample.hs => relational-join-HDBC-pgTest/example/1/querySample.hs