Missing support for relative scss file path resolution in the import part

[dragonation]

It seems there is no support for relative scss file path resolution in the import part if the baseDir set.

For example:
File a/b/c.scss: @import '../../test/test';
File test/_test.scss: a {}

It couldn't find the file test/_test.scss, it will only look the file up in the directory baseDir/../../test, not baseDir/test. What's more, it couldn't deal with the underscore prefix for non-output scss file automatically, to my opinion. However, it seems easy to fix the bug. Working on it, hahaha

[dragonation]

What's more, the sheet pool, or you can say the importedSheets in the Generator couldn't deal with the duplicated files with different relative path description.

For example:

./a.scss
./a/../a.scss

These two files are the same one, but it will be regarded as two different files in the Generator, and import it twice, even more.