Fix failures caused by read-only configuration files

When a configuration file is read only, either due to file ownership or file permissions, the current behavior of the library is to throw. These changes ensure the in-memory configuration is still valid and the error is recoverable.

I didn't include the DLL file in the pull-request; but it needs to be recompiled. Hope you like the changes. Awesome library, by the way; I like the simplicity of the interface from the application side.