Remove white space from lines with only spaces or tabs.

From https://github.com/adobe/brackets/blob/master/src/extensions/default/JSLint/main.js#L75.
Add option lintWSLines to determine if whitespace only lines should be linted.
Rename option to 'skipBlankLines', and change default to false.
Correct if statement due to change of option name.
Merge pull request #2 from Mark-Simulacrum/add-whitespace-option

Optionally skip linting whitespace-only lines.