Use normalize() for consistency in Windows

[mscottx88]

The method getFullPath() does not take into consideration Win32 environments with mixed Posix style require strings.

For instance:

mockRequire(process.cwd() + "/" + path, obj);

In Posix environment the backslash remains, but in Win32 environment, the backslash becomes a forward slash "".

To overcome, wrap the result of getFullPath() with a call to normalize(), exposed by the path module.

[tiagomapmarques]

@mscottx88, was #33 what you had in mind?