add usage to readme.

Author: kdaily

README.md

@@ -8,3 +8,16 @@ Generate HTML usage reports for Synapse projects.
 devtools::install_github("Sage-Bionetworks/synapseusagereports")
 ```
 
+## Usage
+
+### Query the warehouse
+
+```
+./report_data_query.R --project_id=syn1234567 --start_date=2018-01-01 --end_date=2018-03-01 --config_file=~/datawarehouse-config.yml > output.csv
+```
+
+### Generate a report
+
+```
+./render_report.R  --project_id=syn1234567 --team_order='273957' output.csv
+```