Support editorconfig

[crisff11]

Feature: Add support for .editorconfig. Original issue: #138

[okuuva]

Would be extra cool if this supported reading the tab_width and indent_size. From editorconfig home page:

indent_size: a whole number defining the number of columns used for each indentation level and the width of soft tabs (when supported). When set to tab, the value of tab_width (if specified) will be used.
tab_width: a whole number defining the number of columns used to represent a tab character. This defaults to the value of indent_size and doesn't usually need to be specified.

So the priority would be tab_width > indent_size > default.

[heygarrett]

@okuuva I feel like it makes more sense to leave that to the editor, which is presumably already reading from the EditorConfig file.