typo
filter custom directory for IDE-files

While indexing the theme a theme `.idea` is indexed because of the hidden folder PHPstorm creates there. I expanded the existing filter for `blank` and `.git` with `.idea` and refactored the code so more filters can be added easily later.
Would you consider merging this, so I don;t have to edit the Grunt in a local branch? Thanks
Merge pull request #610 from malles/patch-1

filter custom directory for IDE-files
Moved normalization into base, form, button and form component
updated less to 1.7.5
fixed less compile error
Updated jquery in bower.json
correct LESS math calc
wrap test controls in .uk-form
button cleanup
fixed form placeholder color in IE
cleanup form markup in tests
normalized search
normalized close
Updated icon component to Font Awesome to 4.2.0
typo
cleanup tests js
Fixes #573
updated version
Merge branch 'master' of github.com:uikit/uikit

Conflicts:
	CHANGELOG.md