Fixing "Failed to move to new PID namespace: Operation not permitted" being fatal error.

Travis uses OpenVC containers which are not compatible with the chrome sandbox
trying to move itself to it's own PID namespace. We instead use a custom chrome
sandbox which doesn't think this is a fatal issue.
Disabling the default apps, extensions and plugins for more reliable startup.
Making the fail error message more readable.

Old output
---------------------------------------------------------------------
borderRadius at index 0 failed undefined borderRadius
Value - ["calc",0,"px",2.5,"%"], Expected - [[0,"px"]]
Expected value "0,px" did not match
  Element 1 - assert_equals: expected "string" but got "number"
  Element 0 - assert_equals: expected "number" but got "string"
  Number of elements don't match
---------------------------------------------------------------------

New output
---------------------------------------------------------------------
Element div#borderRadius at index 0 failed
 Property borderBottomRightRadius
  Actual - ["calc",0,"px",2.5,"%"]
  Expectation [0,"px"] did not match
   Number of elements don't match
   Element 0 - assert_equals: expected "number" but got "string"
   Element 1 - assert_equals: expected "string" but got "number"
---------------------------------------------------------------------
Border Radius interpolation now works under Chrome.
Chrome now supports sub-pixel font sizes.
Disable beta.