Resolve #156 Incompatible with Localstack (#180)

* Making it so alternative hosts are used when the host parameter is used instead of only when the region is set to local. This will improve compatibility with other methods of mocking AWS services while maintaining compatbility with existing scripts since the host parameter was only used for this mode anyway.

* Update dynamodump.py

Updating help text per requested change.

README.md

@@ -201,6 +201,7 @@ dynamodump -a tar -b some_s3_bucket -m restore -r us-east-1 -p profile -d destin
 ## Local example
 
 The following assumes your local DynamoDB is running on localhost:8000 and is accessible via 'a' as access/secret keys.
+You must specify the host to get local behavior.
 
 ```
 dynamodump -m backup -r local -s testTable --host localhost --port 8000 --accessKey a --secretKey a

dynamodump/dynamodump.py

@@ -36,7 +36,6 @@
 DEFAULT_PREFIX_SEPARATOR = "-"
 CURRENT_WORKING_DIR = os.getcwd()
 JSON_INDENT = 2
-LOCAL_REGION = "local"
 LOCAL_SLEEP_INTERVAL = 1  # seconds
 LOG_LEVEL = "INFO"
 MAX_BATCH_WRITE = 25  # DynamoDB limit
@@ -1121,12 +1120,11 @@ def main():
         "-r",
         "--region",
         help="AWS region to use, e.g. 'us-west-1'. "
-        "Can use AWS_DEFAULT_REGION for local testing.  Use '"
-        + LOCAL_REGION
-        + "' for local DynamoDB testing",
+        "Can use any region for local testing",
     )
     parser.add_argument(
-        "--host", help="Host of local DynamoDB [required only for local]"
+        "--host",
+        help="Host of local DynamoDB. This parameter initialises dynamodump for local DynamoDB testing [required only for local]",
     )
     parser.add_argument(
         "--port", help="Port of local DynamoDB [required only for local]"
@@ -1250,7 +1248,7 @@ def main():
         sys.exit(1)
 
     # instantiate connection
-    if args.region == LOCAL_REGION:
+    if args.host:
         conn = _get_aws_client(
             service="dynamodb",
             access_key=args.accessKey,