Add test coverage macros (#104)

* Add coverage features and add it, laboriously, to everything

* Fix easy tests

* Add tests for != operators

* Clean up test framework a little

* Add documentation of coverage macros

* Fix tests for mat4 to quaternion

* Slightly improve formatting of coverage output

* Trailing whitespace must die

.editorconfig

@@ -0,0 +1,9 @@
+root = true
+
+[*.{c,cpp,h}]
+charset = utf-8
+indent_style = space
+indent_size = 4
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true