Links in notebooks are broken

[cshanahan1]

The link to the drizzlepac handbook is broken in the aligning multiple visits notebooks, so I'd imagine this occurs in other notebooks as well.

[rjavila]

I found another on in the WFPC2 notebook, step 2.

[catherine-martlin]

List of notebooks to check over for broken links:

• [x] Initialization
• [x] align_mosaics (appendix b of the handbook)
• [x] align_multiple_visits (prior example, handbook link, distortion reference file link)
• [x] align_sparse_fields
• [x] align_to_catalogs
• [x] drizzle_wfpc2 (example missing, second missing example, Appendix B handbook)
• [x] mask_satellite (Update link to ACS handbook,
• [x] optimize_image_sampling (Update link to WFC3 handbook, HST dither handbook, update drizzle handbook link)
• [x] sky_matching
• [x] use_ds9_regions_in_tweakreg (prior example link, drizzlepac page link,
• [x] using_updated_astrometry_solutions... (Initialization link)

[catherine-martlin]

See PR #127 for current progress