Switch to new RVM setup files

Auto generated with: rvm rvmrc to .ruby-version
More information: https://rvm.io/workflow/projects/#ruby-versions
Warning message from terminal:
You are using '.rvmrc', it requires trusting, it is slower and it is
not compatible with other ruby managers,
you can switch to '.ruby-version' using 'rvm rvmrc to [.]ruby-version'
or ignore this warnings with 'rvm rvmrc warning ignore
/Users/z/project/wmf/browsertests/.rvmrc',
'.rvmrc' will continue to be the default project file in RVM 1 and RVM
2,
to ignore the warning for all files run 'rvm rvmrc warning ignore
all.rvmrcs'.

Change-Id: I2f4282c9d508fd6f5118ad4b1fb41c67efa5ead9
Merge "Switch to new RVM setup files"