Sync version number to 2.5.0.pre
[55016218] tube rack slots has different tubes in spec
[55016218] remove tube association with other possible tube_rack

before saving it
fix missing requirement
version bumped to 2.5.1.pre
Use id_for instead of id_for!
Bump version
Bump version to 1.9.2
Merge pull request #48 from llh1/development

Merge UAT back to development