Add env to travis

Author: dns2utf8

.travis.yml

@@ -24,6 +24,7 @@ matrix:
     - env: IMAGE=x86_64-gnu-nopt
     - env: IMAGE=x86_64-gnu-make
     - env: IMAGE=x86_64-gnu-llvm-3.7 ALLOW_PR=1 RUST_BACKTRACE=1
+    - env: IMAGE=x86_64-gnu-grammartest
     - env: IMAGE=x86_64-musl
 
     # OSX builders

src/ci/docker/README.md

@@ -1,8 +1,15 @@
 # Testing containers locally
 
+Make sure, you have all required modules unpacked:
+```
+git submodule update --init
+```
+
 Use the `run.sh` from `src/ci/docker`.
 The `src/ci/run.sh` is used inside the container.
 
 ```
-./run.sh x86_64-gnu-grammartest
+src/ci/docker/run.sh x86_64-gnu-grammartest
 ```
+
+You can choose one of the targes from `src/ci/docker`.