Changed chdir to block

This restores the older diretory
after running rake. Closes #19
Merge pull request #22 from azizmb/root_dir_fix

Changed chdir to block
Fix for issue #17 for MSeneadza's comment:

BTW, I just tried using v 1.0.13 against a PostgreSQL db. It crashes like this "PG::Error: ERROR: column "1" does not exist
LINE 1: ...erride_fb_pic","users"."id" FROM "users" WHERE "id" IN ("1")"
That "1" is an integer and shouldn't have quotes around it.