v1.0.0.RC4

• #117 Support CA certificates for SSL client authentication
• #118 update go.mod and add go.sum
• #103 fix crash on bsd / darwin with go1.14
• #115 fix error handling when log directory cannot be opened
• #96 support value configuration for increasing counter metrics by arbitrary values from the log data
• #95 support extra field containing JSON data to be used in Webhook templates
• #93 support simple array indexes in webhook_json_selector
• add --disable-exporter-metrics command line argument for disabling some built-in metrics