Finished long run coolant optimization, and separated fuel and coolant optimization into separate files

Added automatic path resolution. This can be useful if using the code in a jupyter notebook where it can be hard to determine absolute paths

Added better error handling in melting and boiling point calculating function, and updated README accordingly

Updated logic for calculating right endmember fractions from the endmember compositions and a given element composition. Previous logic assumed the existence of an element that was in one endmember and not the other to calculate the endmember fraction, but this is not the case in general. Also added preliminary function for computing melting and boiling points

Updated .gitignore to include pytest files, and updated table of contents generating logic to ignore directories listed in the .gitignore

Actually added outputs directories to the git repo. Due to the way git tracks files, these directories are only tracked if they contain files, so they now contain .gitignore files so that they're tracked.