Autocomplete is no longer triggered automatically if the next character is not whitespace or the end of the text view.
Fixed several warnings in the text editor view.

Removed an unused method in the PLEditorViewController interface. PLEditorViewController no longer registers its line number for the NSViewFrameDidChangeNotification. This is now done in PLLineNumberView, removing the undeclared selector warning in PLEditorViewController.
Several improvements to variable underlining.

The underline is now drawn as half-rounded-rect in the PLTextEditorView drawViewBackgroundInRect: method. This subclass now has a property to track the ranges it should underline.

Changes in underlining are more responsive: they are removed immediately after moving the selection outside the variable (changes in PLEditorViewController).
Improved text clarity in tabs.

The titleLayer of PLTabBarItemLayer now uses integral values for its frame, fixing an issue where the text was blurry. Additionally, the PLTabBarItemLayer implements the layer:shouldInheritContentsScale:fromWindow method and returns YES so that the titleLayer switches contentsScale when moving to a new window.
Added a PLAddOnPlugin protocol.

Added a new PLAddOnPluginIntrospection protocol that inherits from the PLAddOnPlugin protocol. It optionally specifies the four public methods from PLPythonIntrospectionController, which now inherits from this protocol. This removes the warnings in PLEditorViewController about using undeclared selectors.
Removed the unused textDidChange: method from PLEditorViewController.
When parsing fails, still try to underline variables from a previously successful parsing.

In the PLEditorViewController underlineText method, check all ranges returned from the introspection controller if parsing failed. If all ranges are the same variable, underline the variable.
Merge branch 'release-0.2' of https://github.com/liasis/liasis into release-0.2