fix(travis-ci): Remove older versions of go (#516)

Remove older versions of go from travis config due to the testing
dependency testify requiring errors.Is which is only available in go
1.13 and above.

Also switch to master from tip which is the new standard for travis
on golang..
1 file changed
tree: 9ffc2ca3d400cfd75691e957021fbc586715fba0
  1. .github/
  2. .travis.yml
  4. README.markdown
  5. go.mod
  6. go.sum
  7. redis/
  8. redisx/