Merge pull request #204 from chadrien/develop

Use cliframework v1.5.* as 1.6 doesn't seem to work
Make use and switch able to take a major version as argument

If a major version is given as argument, use/switch will use the latest
available minor version of this major version

e.g.: You have php 5.5.6 and 5.5.9, `phpbrew use 5.5` will be
equivalent to `phpbrew use 5.5.9`