Changed Linux Performance tuning to System Performance tuning, incorperating File System Tuning.  Removed all sections not related to system tuning.  TODO: Review tuning doc, ensure all links are updated, review removed sections to ensure they are covered in other docs.
Removed links to File System Tuning.  Changed links from Linux Performance Tuning to System Performance Tuning.  TODO: Determine if Scaling needs to be added to the Capacity Planning section.
Added Scaling section to Planning a Cluster document.
removed version tag that was no longer necessary.
changes to Scaling section of Cluster Capacity Planning doc.
Wrapped Horizontal Scaling note in note div, put /etc/rc.local in code markdown, changed open-files to open files, removed text from block code, changed underlined headers to ##
Merge pull request #901 from basho/jc/issue885

Jc/issue885