Added DOST-based tfpws

Here are the major changes in v1.2.0

1. Added tfpws_dost() as a faster tfpws method, implemented by Jared Bryan.
2. Added codes to handle the cases when there is only 1 trace.
3. Added DOST class in core module.
4. Added power2pad() to pad zeros for the nearest length of the power of 2.

Options to specify the signal window

In this release, we added the option to specify window of interest for Selective and Cluster methods. We also moved the rms() function to the utils.py module.

Fix description file missing issue

This should fix the error complaining missing description.md.

Update on package name to StackMaster

This release changes the name of the package to StackMaster.