Unified formatting and refactored Gruntfile.js

#### Unified formatting across files
* indent_style = space
* indent_size = 2
* insert_final_newline = true
* each line within { } to specify single rule

#### Converted all the tabs into spaces
#### Fixed typo in the previous commit at source/attention_seekers/swing.css
#### Refactored Gruntfile.js
Use ```grunt dev ``` to trigger the ```watch``` task. ```watch``` in turn invokes the ```default``` task.

***PS: each line within { } to specify single rule*** might be reverted back