(#14) Made required configurations: token, repo, user, and tag

[llorllale]

This PR:

• closes Upload.java:45-47: The following configurations must be... #14
• Makes required these configurations: token, repo, user, and tag
• Leaves puzzle for making sure name is not set if if's not configured
• Leaves puzzle for refactoring related to the user config

[codecov]

Codecov Report

Merging #15 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##           master    #15   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           1      1           
  Lines          42     42           
  Branches        3      3           
=====================================
  Hits           42     42

Impacted Files	Coverage Δ
...java/org/llorllale/mvn/plgn/releasecat/Upload.java	100% <ø> (ø)	⬆️

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