Update branch name to "main" in README/LANGUAGE_BINDINGS (#8727)

Summary:
While we're at it, also update the links to Travis (.org to .com).

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8727

Reviewed By: jay-zhuang

Differential Revision: D30675223

Pulled By: ltamasi

fbshipit-source-id: ce4b04a72e56ad35b6bddb982cca41fa8ceacf84

LANGUAGE-BINDINGS.md

@@ -1,6 +1,6 @@
 This is the list of all known third-party language bindings for RocksDB. If something is missing, please open a pull request to add it.
 
-* Java - https://github.com/facebook/rocksdb/tree/master/java
+* Java - https://github.com/facebook/rocksdb/tree/main/java
 * Python
     * http://python-rocksdb.readthedocs.io/en/latest/
     * http://pyrocksdb.readthedocs.org/en/latest/ (unmaintained)

README.md

@@ -1,8 +1,8 @@
 ## RocksDB: A Persistent Key-Value Store for Flash and RAM Storage
 
 [![CircleCI Status](https://circleci.com/gh/facebook/rocksdb.svg?style=svg)](https://circleci.com/gh/facebook/rocksdb)
-[![TravisCI Status](https://travis-ci.org/facebook/rocksdb.svg?branch=master)](https://travis-ci.org/facebook/rocksdb)
-[![Appveyor Build status](https://ci.appveyor.com/api/projects/status/fbgfu0so3afcno78/branch/master?svg=true)](https://ci.appveyor.com/project/Facebook/rocksdb/branch/master)
+[![TravisCI Status](https://api.travis-ci.com/facebook/rocksdb.svg?branch=main)](https://travis-ci.com/github/facebook/rocksdb)
+[![Appveyor Build status](https://ci.appveyor.com/api/projects/status/fbgfu0so3afcno78/branch/main?svg=true)](https://ci.appveyor.com/project/Facebook/rocksdb/branch/main)
 [![PPC64le Build Status](http://140-211-168-68-openstack.osuosl.org:8080/buildStatus/icon?job=rocksdb&style=plastic)](http://140-211-168-68-openstack.osuosl.org:8080/job/rocksdb)
 
 RocksDB is developed and maintained by Facebook Database Engineering Team.
@@ -17,7 +17,7 @@ and Space-Amplification-Factor (SAF). It has multi-threaded compactions,
 making it especially suitable for storing multiple terabytes of data in a
 single database.
 
-Start with example usage here: https://github.com/facebook/rocksdb/tree/master/examples
+Start with example usage here: https://github.com/facebook/rocksdb/tree/main/examples
 
 See the [github wiki](https://github.com/facebook/rocksdb/wiki) for more explanation.