Fix invalid viewport meta

Using ; to separate viewport meta contents will generate the following
error:

Viewport argument value "device-width;" for key "width" not recognized.
Content ignored.

Use , instead fixes that:
http://royaltutorials.com/viewport-argument-value-device-width-for-key-width-not-recognized-content-ignored/
Merge pull request #5 from jjgod/e016cdb51b1ccbfd6a32814211fde36d14eadc3d

Fix meta viewport warnings