[Travis/Test] Clean up and modularization

- Properly setup build matrix
- Clean up .travis.yml
- Try building with Boost 1.57 and Boost 1.58
- Install dependencies to the deps/ subdirectory
- Reduce memory usage of test/type.cpp
- Re-enable some Fusion tests

test/string.cpp

@@ -295,6 +295,14 @@ int main() {
         static_assert(has_operator<String, decltype(greater_equal)>{}, "");
 
         // laws
+        auto strings = make<Tuple>(
+            BOOST_HANA_STRING(""),
+            BOOST_HANA_STRING("a"),
+            BOOST_HANA_STRING("ab"),
+            BOOST_HANA_STRING("abc"),
+            BOOST_HANA_STRING("ba"),
+            BOOST_HANA_STRING("abd")
+        );
         test::TestOrderable<String>{strings};
     }