Add main COOPS API for metadata

[SorooshMani-NOAA]

Fixes #110

Currently the COOPS module uses COOPS's NWS product to get the station metadata:
https://access.co-ops.nos.noaa.gov/nwsproducts.html?type=current

This url doesn't have information about some of the stations. We need to use the main metadata URL:
https://api.tidesandcurrents.noaa.gov/mdapi/prod/webapi/stations.json
see documentation at https://api.tidesandcurrents.noaa.gov/mdapi/prod/

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (1f79507) 90.04% compared to head (43d5699) 90.18%.

Files	Patch %	Lines
searvey/coops.py	94.44%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #123      +/-   ##
==========================================
+ Coverage   90.04%   90.18%   +0.13%     
==========================================
  Files          13       13              
  Lines        1015     1049      +34     
  Branches      151      155       +4     
==========================================
+ Hits          914      946      +32     
- Misses         55       56       +1     
- Partials       46       47       +1     

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[pmav99]

Looks good. I would just rename the tests from old/new to nws/main.

[SorooshMani-NOAA]

Thanks for your feedback. I also realized I haven't updated stations API call to the main API, I'll update that as well and when everything passes I'll merge.