Fix for #63 by using replace() instead of lstrip()

I made this pull request because I'm experiencing the bug as of issue #63 (in 0.1.13 tagged version and also in master branch)

I think that the problem is the use of lstrip() instead of replace()

In case we have base_path="api/v1/" and path="api/v1/auth_token" resource path becomes "uth_token" because lstrip() strips all the 'a' characters.

Thanks