add tests for not expressions
Update README.md

Code formatting.
adding tests for string length function
Revert "adding tests for string length function"

This reverts commit eccfdf4fffdd8cb9ac8cc0833f37eb6566198e3f.
adding string length function tests
Merge pull request #15 from rmariuzzo/patch-1

Update README.md
Merge pull request #13 from mgreter/master

Adds IE test for css expressions
Merge pull request #17 from wonja/str_length_tests

Str length tests
adding BEM selector tests
Merge pull request #18 from wonja/bem_selector_tests

adding BEM selector tests
string insert, index, slice, and case conversion tests
Merge pull request #19 from wonja/str_function_tests

yay even more stuff

string insert, index, slice, and case conversion tests
Interpolants in css imports tests
Merge pull request #20 from wonja/interpolants_in_css_imports_tests

Interpolants in css imports tests
wrapped pseudo selector tests
Tests for allowing a trailing comma at the end of a list
Merge pull request #21 from wonja/wrapped_pseudo_selectors

wrapped pseudo selector tests
Merge pull request #22 from wonja/trailing_comma_list

Tests for allowing a trailing comma at the end of a list
tests for interchangeability of - and _
Merge pull request #24 from wonja/interchangeable_hyphens_underscores

tests for interchangeability of - and _