feat: Add AWS credential parameters to create_client()

- Add aws_access_key_id, aws_secret_access_key, aws_session_token, and region_name parameters
- Pass credentials through to S3StorageAdapter and boto3.client()
- Enables multi-tenant scenarios with different AWS accounts
- Maintains backward compatibility (uses boto3 default credential chain when omitted)
- Add comprehensive tests for credential handling
- Add examples/credentials_example.py with usage examples

Fixes credential conflicts when multiple SDK instances need different credentials.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

README.md

@@ -12,11 +12,11 @@
 
 **Store 4TB of similar files in 5GB. No, that's not a typo.**
 
-DeltaGlider is a drop-in S3 replacement that achieves 99.9% compression for versioned artifacts, backups, and release archives through intelligent binary delta compression.
+DeltaGlider is a drop-in S3 replacement that may achieve 99.9% size reduction for versioned compressed artifacts, backups, and release archives through intelligent binary delta compression (via xdelta3).
 
 ## The Problem We Solved
 
-You're storing hundreds of versions of your releases. Each 100MB build differs by <1% from the previous version. You're paying to store 100GB of what's essentially 100MB of unique data.
+You're storing hundreds of versions of your software releases. Each 100MB build differs by <1% from the previous version. You're paying to store 100GB of what's essentially 100MB of unique data.
 
 Sound familiar?
 
@@ -435,8 +435,8 @@ DeltaGlider uses a clean hexagonal architecture:
 - Any versioned binary data
 
 ❌ **Not ideal for:**
-- Already compressed unique files
-- Streaming media files
+- Already compressed **unique** files
+- Streaming or multimedia files
 - Frequently changing unstructured data
 - Files smaller than 1MB