Fix cursor so clicking the below the last line of text puts the cursor at
the end of the last line.
Fix cursor not being able to move within the last line of text.
Never break when past the last row
Set targetLeft to Infinity when past last row
Add spec for clicking past last line
Mention single click
Merge pull request #3867 from atom/ks-select-past-last-line

Fix selecting past the last line