Migrate to gh-actions

[majst01]

Travis is going to die, gh actions are mature now.

@rhajek i tried to migrate the deploy-snapshot actions to my best knowledge, please check.

[codecov-io]

Codecov Report

Merging #720 (0644513) into master (19f9ea9) will decrease coverage by 0.82%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master     #720      +/-   ##
============================================
- Coverage     52.75%   51.92%   -0.83%     
+ Complexity      363      356       -7     
============================================
  Files            69       69              
  Lines          2540     2540              
  Branches        266      266              
============================================
- Hits           1340     1319      -21     
- Misses         1135     1158      +23     
+ Partials         65       63       -2     

Impacted Files	Coverage Δ	Complexity Δ
.../influxdb/msgpack/MessagePackConverterFactory.java	0.00% <0.00%> (-100.00%)	0.00% <0.00%> (-3.00%)
...uxdb/msgpack/MessagePackResponseBodyConverter.java	0.00% <0.00%> (-25.00%)	0.00% <0.00%> (-1.00%)
src/main/java/org/influxdb/impl/InfluxDBImpl.java	75.17% <0.00%> (-3.88%)	74.00% <0.00%> (-3.00%)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 19f9ea9...0644513. Read the comment docs.