Cleanup and feedbacks changes

[Ashmita152]

Signed-off-by: Ashmita Bohara ashmita.bohara152@gmail.com

Which problem is this PR solving?

Part of https://github.com/jaegertracing/jaeger-client-python/issues/295

Short description of the changes

• Removes gh-3 tags
• Removes travis.yml and install-crossdock-deps.sh script which was used to setup a particular version of docker-compose
• Prevents double build of crossdock image by reusing existing tag.

[codecov[bot]]

Codecov Report

Merging #298 (d3cfeba) into master (6bf76a1) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #298   +/-   ##
=======================================
  Coverage   95.91%   95.91%           
=======================================
  Files          25       25           
  Lines        1935     1935           
  Branches      265      265           
=======================================
  Hits         1856     1856           
  Misses         52       52           
  Partials       27       27           

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[Ashmita152]

Minor cleanup for Dockerfile:

• COPY can accept multiple source files (ref: https://docs.docker.com/engine/reference/builder/#copy)
• WORKDIR should create directory if it doesn't exist (ref: https://docs.docker.com/engine/reference/builder/#workdir)
• pip can be passed multiple -r options (ref: https://pip.pypa.io/en/stable/reference/pip_install/#cmdoption-r)

Less number of intermediate layers means faster build of docker images.