Change ctrl-a binding to editor:move-to-first-character-of-line

Considering that the entire Atom core team has ctrl-a bound to move to
the first character and it's also the the default behavior of Sublime,
this seems like a more sensible and useful default option even though
it deviates from text editing norms on OS X.
Use event methods for theme subscriptions
Use event methods in EditorComponent
Add KeymapManager::onDidLoadBundledKeymaps
Use the new split*() methods on Pane model in WorkspaceView specs
Add ThemeManager::onDidUpdateStylesheet
Move global editor stylesheet updating into the ThemeManager
Subscribe to items via event methods. 

Add deprecation warnings when they don’t return a disposable
nof
Fix / clean up specs
Upgrade to language-ruby@0.36
Move the deprecations
Merge pull request #3514 from atom/bo-remove-method-deprecations

Remove event deprecations from core
Deprecate font-size, font-family, line-height methods on EditorView.
Deprecate EditorView::setShowIndentGuide
Deprecate setShowInvisibles
Prepare 0.128
Merge pull request #3518 from atom/bo-font-settings-in-model

Deprecate font-size, font-family, line-height, invisibles, indent guide methods on EditorView
Upgrade first-mate with new docs
Upgrade to wrap-guide@0.22