Merge pull request #1 from google/master

Merge updates from source repo.
Fix & improve building doc.
Fix/improve building doc.
Fix/improve building doc.
Fix/improve building doc.
Fix/improve building doc.
Properly format text to 80 cols limit in building doc.
Remove obsolete reference to Wear SDK from building doc.
Update Wear SDK tag reference in building doc (4.4W > 4.4W2).
Merge pull request #74 from eyecatchup/master

Update BUILDING.md