Merge pull request #27 from mattnovelli/master

Help message blurb

Author: patrickbr

README.md

@@ -61,7 +61,7 @@ This suite consists of several tools:
 * `octi`, create a schematic version of a line graph
 * `transitmap`, render a line graph into an SVG map (`--render-engine=svg`) or into vector tiles (`--render-engine=mvt`)
 
-All tools output a graph, in the GeoJSON format, to `stdout`, and expect a GeoJSON graph at `stdin`. Exceptions are `gtfs2graph`, where the input is a GTFS feed, and `transitmap`, which writes SVG to `stdout` or MVT vector tiles to a specified folder.
+All tools output a graph, in the GeoJSON format, to `stdout`, and expect a GeoJSON graph at `stdin`. Exceptions are `gtfs2graph`, where the input is a GTFS feed, and `transitmap`, which writes SVG to `stdout` or MVT vector tiles to a specified folder. Running a tool with `-h` will show a help message with all allowed options.
 
 The `example` folder contains several overlapping-free line graphs.