path: resolve normalize drive letter to lower case

make path.resolve work the same as path.normalize.

see https://github.com/joyent/node/blob/v0.12/lib/path.js#L180
If we're normalizing paths, then as mentioned before, we need to normalize `cwd()` output, and thus reach consistency.
Anyway drive letter case is arbitrary, and depends only on the process's environment.
```
C:\>node -e console.log(process.cwd())
C:\

C:\>cmd /k cd "c:\temp"

c:\temp>node -e console.log(process.cwd())
c:\temp


```
It is semantically equivalent, but breaks allot of path comparisons as they are string based and case sensitive.