Make the server check for correct SERVER_URL format

[jgomo3]

Only when trying to save a form, the client app receive the current Error:

Error: The remote URL must contain the version: <The SERVER_URL value>

I propose to give this warning or produce an error during server startup.

The code that make the checking in the client and throws the exception is in the kinto-client library

[almet]

Hi,

This is indeed a good idea!
Would you like to work on a fix?

[jgomo3]

I'll give it a try. Sure I'll have some questions in the path while I get familiar with the code.

[jgomo3]

I created a pull request: #199

I would like to discuss it.