Add CI with code coverage using Travis CI and Codecov

.luacov

@@ -0,0 +1,3 @@
+modules = {
+  ["serpent"] = "src/serpent.lua"
+}

.travis.yml

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+language: python
+sudo: false
+
+env:
+  - LUA="lua=5.1"
+  - LUA="lua=5.2"
+  - LUA="lua=5.3"
+  - LUA="luajit=2.0"
+  - LUA="luajit=2.1"
+
+before_install:
+  - pip install codecov
+  - pip install hererocks
+  - hererocks lua_install --$LUA -r latest
+  - source lua_install/bin/activate
+  - luarocks install cluacov
+
+install:
+  - luarocks make
+
+script:
+  - lua -lluacov t/test.lua
+
+after_script:
+  - luacov
+  - codecov -X gcov

README.md

@@ -1,5 +1,8 @@
 # Serpent
 
+[![Build Status](https://travis-ci.org/pkulchenko/serpent.svg?branch=master)](https://travis-ci.org/pkulchenko/serpent)
+[![Coverage status](https://codecov.io/gh/pkulchenko/serpent/branch/master/graph/badge.svg)](https://codecov.io/gh/pkulchenko/serpent)
+
 Lua serializer and pretty printer.
 
 ## Features