ORC-745: Update README.md with new travis-ci.com links (#638)
ORC-745: Update README.md with new travis-ci.com links (#638)

### What changes were proposed in this pull request?

This PR aims to update README.md with new travis-ci.com links.

### Why are the changes needed?

https://issues.apache.org/jira/browse/INFRA-21354 migrated Apache ORC Travis CI from travis-ci.org to travis-ci.com.

### How was this patch tested?

1. Since we migrated, travis-ci.com is triggered on this PR correctly.
   - https://travis-ci.com/github/apache/orc/builds/214961084
2. Manually click the new links.
apache/orc,apache/orc,omalley/orc,apache/orc,omalley/orc,apache/orc,apache/orc,omalley/orc,omalley/orc,omalley/orc,apache/orc,apache/orc,apache/orc,omalley/orc,omalley/orc