travis: used different compiler to run test. (#235)

* travis: specified language.
* test: added test cases for `core.table`.

.travis.yml

@@ -12,9 +12,7 @@ matrix:
           - $HOME/Library/Caches/Homebrew
           - /usr/local/Homebrew
 
-compiler:
-  - gcc
-  - clang
+language: c
 
 addons:
   apt:

t/core/table.t

@@ -0,0 +1,31 @@
+use t::APISix 'no_plan';
+
+repeat_each(2);
+no_long_string();
+no_root_location();
+
+run_tests;
+
+__DATA__
+
+=== TEST 1: sanity
+--- config
+    location /t {
+        content_by_lua_block {
+            local core = require("apisix.core")
+            local t = {"first"}
+            core.table.insert_tail(t, 'a', 1, true)
+
+            ngx.say("encode: ", core.json.encode(t))
+
+            core.table.set(t, 'a', 1, true)
+            ngx.say("encode: ", core.json.encode(t))
+        }
+    }
+--- request
+GET /t
+--- response_body
+encode: ["first","a",1,true]
+encode: ["a",1,true,true]
+--- no_error_log
+[error]