Add additional field to github issue template. (#645)

* Add additional field to github issue template.

Request the command line flags to the exporter.

* Update version flag for kingpin.

.github/ISSUE_TEMPLATE.md

@@ -19,9 +19,12 @@
 -->
 ### Host operating system: output of `uname -a`
 
-### node_exporter version: output of `node_exporter -version`
+### node_exporter version: output of `node_exporter --version`
 <!-- If building from source, run `make` first. -->
 
+### node_exporter command line flags
+<!-- Please list all of the command line flags -->
+
 ### Are you running node_exporter in Docker?
 <!-- Please note the warning above. -->