Minor readme edits

[iambmelt]

This PR

• Removes old announcements from previous versions
• Updates the version string in the gradle snippet
• Removes the roadmap section, which has not been kept up-to-date

[codecov-commenter]

Codecov Report

Merging #1735 (c8ea78b) into dev (3ac3354) will not change coverage. The diff coverage is n/a.

:exclamation: Current head c8ea78b differs from pull request most recent head a10b5f4. Consider uploading reports for the commit a10b5f4 to get more accurate results

@@            Coverage Diff            @@
##                dev    #1735   +/-   ##
=========================================
  Coverage     48.89%   48.89%           
  Complexity      367      367           
=========================================
  Files            60       60           
  Lines          2712     2712           
  Branches        331      331           
=========================================
  Hits           1326     1326           
  Misses         1235     1235           
  Partials        151      151           

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