travis: don't recurse submodules

libgit2 has (intentionally) broken submodules.  turn off travis' default
submodule recursion, lest we go into the broken ones.

Author: ethomson

.travis.yml

@@ -1,3 +1,6 @@
+git:
+ submodules: false
+
 language: c
 
 os:
@@ -12,6 +15,7 @@ before_install:
  - date -u
  - uname -a
  - env | grep -v "BINTRAY_API_KEY" | sort
+ - git submodule update --init
 
 install: true