v1.1.0

1. added support for vacuum (zero-density) initial conditions and solutions
2. added support for zero-temperature/pressure initial conditions and solutions
3. fixed some math errors in computing the speed of the gas-vacuum free boundary
4. added more test examples to reflect the power of this code
5. improved the plotting style

v1.0.1

Corrected a bug and improved the plotting code by adding the name of each wave.

v1.0.0

Compute the exact Riemann solution of the 1D compressible Euler equations (only for ideal polytopic gas) and store key physical quantities so that the exact solution at any point can be retracted using these quantities. Good and easy-to-use enough for plotting, code verifying and teaching. Vacuum states are supported (zero density) and the speed of the free boundary between the fluid and the vacuum can be produced. States with zero temperature are not supported yet.