Rename `pg_getrecord()`

This addresses issue #32 and changes the function name from `pg_get_record()` to `pg_get_record()`. Additionally, this changes the file name in the same manner `pg_getrecord.R` -> `pg_get_record.R` and updates the example to use the renamed function.

This might need a little manual merging once the other PRs I issued last night are merged as these two commits edit a file changed somewhat in a few of those PRs.