chore(editorconfig): adds editorconfig file

this little file brings pure awesomeness to our project, since
it makes sure that everybody who's developing on it, uses the
right conventions, as long as the developer has a corresponding
editorconfig plugin installed.

these plugins are available for several editors like sublime, vim
and may others.
Merge pull request #6 from angular-leap/editor-config-support

chore(editorconfig): adds editorconfig file