v0.4.0

Major feature updates:

⚠️ These feature changes break the API from v0.3.2 in many ways!

• Custom function support.
• Combined Context type containing variables and functions.
• Vectors and matrices now support calculations as entries.
• The equation solver is now integrated into the evaluation process.
• The evaluator can now handle multiple values at once using combinatorics.
• Moved latex processing to rust libraries (tectonic, mathjax_svg)

Minor bug fixes:

• Got cross product to work properly.

There also now exists a wiki 🎉, which tries to explain the mathematical aspects of the library in depth.