fix: default proto package name is the module name, not ""

[0x2b3bfa0]

Closes #175; please refer to #171 for context.

[codecov]

Codecov Report

Merging #176 (3e61431) into master (6a43682) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #176   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           20        20           
  Lines          862       895   +33     
  Branches       149       163   +14     
=========================================
+ Hits           862       895   +33     

Impacted Files	Coverage Δ
proto/modules.py	100.00% <ø> (ø)
proto/_package_info.py	100.00% <100.00%> (ø)
proto/enums.py	100.00% <100.00%> (ø)
proto/marshal/collections/repeated.py	100.00% <100.00%> (ø)
proto/marshal/marshal.py	100.00% <100.00%> (ø)
proto/message.py	100.00% <100.00%> (ø)

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[parthea]

I've opened #309 as the branch in this PR is no longer active.