build: Test in TypeScript 2.8 (#48)

* build: update mocha to 5.0.5
* ci: test in TypeScript 2.8
* docs: update readme

Author: teppeis

.travis.yml

@@ -15,6 +15,8 @@ script:
   - npm test
   - npm install --no-save [email protected]
   - npm test
+  - npm install --no-save [email protected]
+  - npm test
   - npm install --no-save typescript@latest
   - npm test
 cache:

README.md

@@ -11,7 +11,7 @@ espower-typescript
 
 ## TypeScript versions
 
-* espower-typescript v8.x uses TypeScript from v2.2 to v2.7
+* espower-typescript v8.x uses TypeScript from v2.2 to v2.8
 * espower-typescript v7.x uses TypeScript v2.1
 * espower-typescript v6.x uses TypeScript v2.0
 * espower-typescript v5.x uses TypeScript v1.8