Fix some typos in docs (vuejs-templates#331)

Author: sjking

docs/env.md

@@ -44,7 +44,7 @@ As we can see, `test.env` inherits the `dev.env` and the `dev.env` inherits the
 
 ### Usage
 
-It is simple to use the environment variables to your code. For example:
+It is simple to use the environment variables in your code. For example:
 
 ```js
 Vue.config.debug = process.env.DEBUG_MODE

docs/static.md

@@ -12,7 +12,7 @@ Since these assets may be inlined/copied/renamed during build, they are essentia
 
 ### Asset Resolving Rules
 
-- **Relative URLs**, e.g. `./assets/logo.png` will be interpreted as a module dependency. They will be replaced with a auto-generated URL based on your Webpack output configuration.
+- **Relative URLs**, e.g. `./assets/logo.png` will be interpreted as a module dependency. They will be replaced with an auto-generated URL based on your Webpack output configuration.
 
 - **Non-prefixed URLs**, e.g. `assets/logo.png` will be treated the same as the relative URLs and translated into `./assets/logo.png`.
 

docs/structure.md

@@ -60,7 +60,7 @@ Contains e2e test related files. See [End-to-end Testing](e2e.md) for more detai
 
 ### `index.html`
 
-This is the **template** `index.html` for our single page application. During development and builds, Webpack will generate assets, and the URLs for those generated assets will automatically injected into this template to render the final HTML.
+This is the **template** `index.html` for our single page application. During development and builds, Webpack will generate assets, and the URLs for those generated assets will be automatically injected into this template to render the final HTML.
 
 ### `package.json`
 

docs/unit.md

@@ -14,7 +14,7 @@ And the files:
 
 - `index.js`
 
-  This the entry file used by `karma-webpack` to bundle all the test code and source code (for coverage purposes). You can ignore it for the most part.
+  This is the entry file used by `karma-webpack` to bundle all the test code and source code (for coverage purposes). You can ignore it for the most part.
 
 - `specs/`