Merge pull request #271 from timfel/master

Fix for Firefox
bindings: bindings depend on lively.lang.Closure
cmdline search: fix file search in presence of symlinks pointing to nonexisting files
search: improved updating, don't search for old terms
dirviewer: deleteSelectedFileInteractively, createDirInteractively
ObjectEditor: select new method on creation
layouting: saner dropping behavior in presence of placeholders and layouting
morphic anim: fix double invocation
paths: fix path shape bounds when not yet rendered
morph previews: fix extent of preview
sliders: preperation for double-slider (time slider)
l2l / login: small cleanup
Update .travis.yml

Adding slack integration
Travis: Activated debug flag
Travis: Temporary disabling advanced IndexedDB tests (currently failing for Travis)
lib update: html2canvas
layouting: placeholders are removed before drop so that layouting does not accidentally compute layout including placeholders
lazily defining additions of objects in other modules using Module>>runWhenLoaded. This cleans up various places where we had to enforce a certain module order to allow additions / monkey patching to classes
clojure: Clojure.ReplServer, starting and stopping server process, ensuring lein lively profile
clojure: better eval support, clojure mode has now support for clojure spevific keybindings