feat(Documentation/api): add some intro material

add some intro material and normalize the headers to the rest of the
coreos/docs.
chore(Documentation/api): remove some whitespace
feat(Documentation/api): add a statistics section
fix(peer_server.go) init name field and update leader field
fix(docs): reference correct cors flag
fix(docs): reference correct cors flag
fix(docs): suggest cors flag for using dashboard
Merge pull request #449 from xiangli-cmu/fix_stats

fix(peer_server.go) init name field and update leader field
doc(Documentation/libraries-and-tools.md) fix link to clients-matrix
Merge pull request #452 from xiangli-cmu/fix_client-matrix_link

doc(Documentation/libraries-and-tools.md) fix link to clients-matrix
fix(Documentation/api): fixup the names in stats

This was fixed in #449
feat(Documentation/api): document the store statistics
Merge pull request #444 from philips/document-stats-api

Documentation: document the stats API
chore(Documentation/api): introduce acronym later in the text
Merge pull request #455 from philips/fixup-cas-header

chore(Documentation/api): introduce acronym later in the text
Merge pull request #447 from robszumski/master

Prepare docs to be synced to website
Merge remote-tracking branch 'upstream/master'