v0.5.1 Generic type generation

We released the v0.5.1.
This is a breaking upgrade. We rewrote almost the code to make lib generic-type-based.
Now, you can use bigint as meta-calc-part!

The Gaussian-Jordan Algorithm

Whole lib will be faster than before.
We guarantee it will not panic! except the implement for trait Ord failed.

For free variables:
It set all free variables be 1. Because, usually it provides the exactly solution.

New Error Handle solution

We have changed the API.
Now, it is using its own errortype ErrorCases.
We also updated the documentation and added integration tests.

Public API changed

This version is linted by clippy and formated by rustfmt.
But, Public API changed.
You'd better use newest API.

The first OOP version

We have already restructured the Delta-3 parser and added the proper integration tests.
Fixed some bugs that will panic.

First usable version

Now, lib_xch has already separted ftom xch-ceb.
The library is no panic! or println! added, and it's a pure lib.
We also added tests mod. let lib be more stable.