Document and check WCS usage for to_sky option in subset-to-region translator; add tests
#131
| Job | Run time |
|---|---|
| 9s | |
| 19s | |
| 7s | |
| 1m 59s | |
| 1m 42s | |
| 3m 21s | |
| 3m 21s | |
| 3m 48s | |
| 3m 3s | |
| 6m 31s | |
| 6m 41s | |
| 0s | |
| 31m 1s |