Disables filepicker on old Chrome versions

Displays an error dialog if the user tries to mount a local directory, when the version of Chrome does not support this operation.
Factors out version checking into a function
Uses weaker permissions in welcome screen

The welcome screen currently requests permission for read/write access to Drive, in order to display the "open" dialog box.  However, all that is needed to display this dialog is readonly access to metadata.  This commit changes to using this weaker scope.  One feature that does require full drive access is the ability to upload files from the "open" dialog, so this feature is disabled.
Makes upload tab in open dialog optional
Merge pull request #61 from jupyter/scopes

Uses weaker permissions in welcome screen
Moves client IDs to a single file

Creates a new javascript source file that contains all client IDs for the web app.  This file also contains an explanation of the reason for having two client IDs.
Changes client ID for Google Drive access

Changes the client ID used for load/save and realtime access.  This has no affect on users as Google Drive does not are which client ID is used to access it.  Only the Cloud Console project matters, and the new client ID belongs to the same cloud console project as the old on.
Merge pull request #62 from jupyter/clientid

Changes to Client IDs
Changing to use versioned kernels.
Fixing typo.
Update README.md
Override platform in kernel.py.
Don’t use 8888 as default port

caching redirects cause problems with other apps (IPython)
on the same ports.
update version to 8 in manifest
Merge pull request #63 from MatthewTurk/master

Drop zeropy from names, move to versioned, and fix platform
Merge pull request #64 from minrk/not-8888

Don’t use 8888 as default port
Merge pull request #59 from jupyter/filepicker

Disables filepicker on old Chrome versions
Fix typo: verison->version
Merge pull request #65 from mr-c/patch-1

README.md: verison->version
Updates binary version and manifest version

Updates binary version to use newest PNaCl build, and updates manifest version.