logline output buffers rather than updating on every ws message

In builds with lots of output, trying to reload the page partway
through the build results in thousands of websocket messages (one
per line) that each update the DOM.  This can cause the browser to
freeze.  Instead, use requestAnimation frame to delay the DOM
updates.
Merge pull request #146 from movableink/buffer-websocket-log-output

logline output buffers rather than updating on every ws message
Fix gravatar size at build page to fit the stylesheet.
Merge pull request #150 from fudanchii/html-fix

Fix gravatar size at build page to fit the stylesheet.
ability to use custom badges. standard badges now using shields.io
Merge remote-tracking branch 'origin/master'
added git revision to the binary for debugging purposes
Add table of content for README
Add deployment and publish plugin list to README
Merge pull request #151 from fudanchii/docs

Documentation update.
Set author for pull request
Fix pull-request checkout not working for Git >=1.8

Explicitly create pr branch from origin
Merge pull request #155 from fudanchii/pr-author

Set PR commit author from User.Login
Merge branch 'master', remote-tracking branch 'origin'
added section to yaml for custom hostnames
a bit of prep-work for adding caching
added code to persist directories between builds. see issue #147
updated README to include caching details for #147
add 'rebuild' button to rebuild any build that has finished
only allow admins to rebuild commits

This is a check for both whether to display the button and whether to
actually do the rebuild. It slightly modifies RepoAdminHandler so it's
worth a close look.