Add taper processing method

[d-chambers]

Description

This PR adds Patch.taper and its associated docs.

Checklist

I have (if applicable):

• referenced the GitHub issue this PR closes.
• documented the new feature with docstrings or appropriate doc page.
• included a test. See testing guidelines.
• your name has been added to the contributors page (docs/contributors.md).
• added the "ready_for_review" tag once the PR is ready to be reviewed.

[codecov]

Codecov Report

Merging #154 (2ddeb65) into master (a4bf51d) will increase coverage by 0.06%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #154      +/-   ##
==========================================
+ Coverage   96.57%   96.63%   +0.06%     
==========================================
  Files          54       55       +1     
  Lines        3415     3476      +61     
==========================================
+ Hits         3298     3359      +61     
  Misses        117      117              

Flag	Coverage Δ
unittests	96.63% <100.00%> (+0.06%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
dascore/examples.py	100.00% <ø> (ø)
dascore/core/patch.py	98.38% <100.00%> (+0.01%)	⬆️
dascore/proc/__init__.py	100.00% <100.00%> (ø)
dascore/proc/taper.py	100.00% <100.00%> (ø)
dascore/utils/misc.py	97.67% <100.00%> (+0.05%)	⬆️