Include LICENSE in sdist and clarify in README

[mcs07]

• Used a MANIFEST.in file to include the LICENSE file in PyPI sdist, as required by the BSD license.
• Corrected README to say BSD not MIT, so it matches the LICENSE file and setup.py.

[codecov-io]

Codecov Report

Merging #158 into master will increase coverage by 7.41%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #158      +/-   ##
==========================================
+ Coverage   67.57%   74.98%   +7.41%     
==========================================
  Files          28       28              
  Lines        2751     2323     -428     
  Branches      392      392              
==========================================
- Hits         1859     1742     -117     
+ Misses        740      433     -307     
+ Partials      152      148       -4

Impacted Files	Coverage Δ
sentry_sdk/integrations/sanic.py	0% <0%> (-76.67%)	⬇️
sentry_sdk/integrations/aws_lambda.py	0% <0%> (-12.83%)	⬇️
sentry_sdk/_compat.py	84% <0%> (+3.23%)	⬆️
sentry_sdk/hub.py	79.67% <0%> (+4.02%)	⬆️
sentry_sdk/worker.py	87.34% <0%> (+4.2%)	⬆️
sentry_sdk/integrations/flask.py	75.49% <0%> (+4.84%)	⬆️
sentry_sdk/integrations/excepthook.py	86.36% <0%> (+6.36%)	⬆️
sentry_sdk/integrations/django/__init__.py	79.5% <0%> (+7.83%)	⬆️
sentry_sdk/scope.py	75% <0%> (+8.05%)	⬆️
sentry_sdk/integrations/rq.py	78% <0%> (+9.03%)	⬆️
... and 12 more

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[untitaker]

thanks, I will merge as soon as the build is green

[untitaker]

@mcs07 do you need a new release for this?

[mcs07]

No it's not urgently needed, thanks.