Cannot override default endpoint during compilation

[mfb2]

When compiling the application, Forcex.Client uses the default endpoint of login.salesforce.com to generate services & objects. When attempting to use sandbox / test credentials, compilation fails because there is no ability to change this endpoint to test.salesforce.com.

#26 attempts to resolve this issue, please review and advise.

[mfb2]

I updated #26 to rely on the configuration provided to the :login method and/or system environment variables. compile.forcex.ex remains unchanged for the moment, relying on default configuration to do its work.