travis: Remove node 0.8, add node 0.10

Travis is failing on two accounts:

* "Error: No compatible version found: minimatch@'^0.3.0'"
  (because the version of npm that shipped with 0.8 doesn't
  support ^

* npm WARN engine stringify-object@0.1.8: wanted: {"node":">=0.10.0"}
  (current: {"node":"v0.8.26","npm":"1.2.30"})
  npm WARN engine has-color@0.1.7: wanted: {"node":">=0.10.0"}
  (current: {"node":"v0.8.26","npm":"1.2.30"})
  npm WARN engine configstore@0.2.3: wanted: {"node":">=0.10.0"}
  (current: {"node":"v0.8.26","npm":"1.2.30"})
  npm WARN engine object-assign@0.1.2: wanted: {"node":">=0.10.0"}
  (current: {"node":"v0.8.26","npm":"1.2.30"})

Closes gh-1258
Dialog: Fix shift-tab handling, focus the correct element

Copy-paste error introduced in df6110c0d424ff3306fdd5576011f2dcf4d242d0

Updates the tabbing test to be more specific about which element should
have focus, instead of only checking if focus is within the dialog.

Ref #9646
Ref #10103
Closes gh-1264
Dialog: Honor preventDefault when managing focus

If event.isDefaultPrevented() is true, the focus management is
completely skipped, assuming the user manages focus manually.

Fixes #10103
Closes gh-1265
Datepicker: Define en and en-US locales based on defaults

Fixes #6682
Closes gh-1269