Upgrade brightray
OVERRIDE => override in native_window.h
Prevent creating popup window from inside WebContents
OVERRIDE => override in atom_api_window.h
Set "defaultPrevented" when "preventDefault()" is called
Route window.open to "new-window" event
Add "frameName" as paramter for "new-window" event
spec: "new-window" event of <webview>
Use GuestWindowManager to mange windows created by window.open
spec: "new-window" event of BrowserWindow
Add focus() and blur() for FakeWindow
Add eval() for FakeWindow
doc: "new-window" event of WebContents
Make <a target="_blank"> open window by default
Don't throw exception on closed guest window
spec: Only test net.connect on Mac

The Linux travis ci machine is quite unstable on this test.
Reuse the window of same frame name
Simplify the GuestWindowManager

Instead of recording guest explicitly in a map, we just make use of
closure for bookkeeping.
Merge pull request #750 from atom/fix-leaking-webcontents

Handle window.open and <a target="..."> correctly