feat(path): add support for changing path

### Current behavior
Only the filename/path relative to base can be changed. Specifying a new name which includes a path moves the file into a subdirectory relative to base.

Given: "test/fixtures/hello.txt" and rename("test/elsewhere/hello.txt") results in "test/fixtures/test/elsewhere/hello.txt"

Hacking with '..' such as rename("../elsewhere/hello.txt") results in path.join(file.base, file.cwd, "test/elsewhere/hello.txt")

When called as rename(function(dir, base, ext) {...}), dir cannot be modified while base and ext can.

### Desired behavior
Support for modifying the relative path from CWD. Specifying a new name which includes a path moves the file into a subdirectory relative to CWD.

Given: "test/fixtures/hello.txt" and rename("test/elsewhere/hello.txt") results in "test/elsewhere/hello.txt"

When called as rename(function(dir, base, ext) {...}), dir can be modified along with base and ext.

### Other
I bumped the version in a separate commit. Feel free to ignore.