Minor suggestions for the IMA Manual Correction Notebook

[FDauphin]

Here are a few suggestions for the notebook "Correcting for Scattered Light in WFC3/IR Exposures: Manually Subtracting Bad Reads" that weren't able to be addressed before merging #45 :

• Add "6. Drizzling Nominal and Reprocessed FLT Products" to the table of contents
• Change "6. Conclusions" to "7. Conclusions" in the table of contents
• In code block 7 and 8, the same object is defined as raw_file and raw_filepath. Just use the latter since it matches the style of the other variables
• Under "6. Drizzling Nominal and Reprocessed FLT Products", use backticks for filenames, e.g. ipppssoot
• Put the imports at "6. Drizzling Nominal and Reprocessed FLT Products" under "1. Imports" with an appropriate reason for calling the libraries

[FDauphin]

Also add to the learning goals:

• Compare the original DRZ to the reprocessed DRZ image.

[FDauphin]

All comments were addressed in #78.