MultiMarkdownParser: search for executable in full $PATH

It’s the class’ responsibilty anyway, not that of the wrappers. Should
smoothen usage of the Automator action significantly.
Build system: fine tune Rake::MustacheTask
Build system: rename :package task to :zip

Because that is what I always type first anyway…
README clarifications
Conform UTIs to public.text, not public.plain-text

public.plain.txt is for text without markup, as per
https://developer.apple.com/library/ios/documentation/Miscellaneous/Refe
rence/UTIRef/Articles/System-DeclaredUniformTypeIdentifiers.html
Build system: requirements for package build tasks

Assume less, require more.
Build system: SmartFileTask

Factor commonly grouped file tasks out into a class.
Build system: refactor MustacheTask to use SmartFileTask
De-hardcode more Platypus template data
Build system: ZipTask
Build system: use ZipTask for package zipping
Build system: dynamical data generators in MustacheTask

Allowing Proc / Lambda @data should enable dynamic data generation
without resorting to before / after hook hacks.
Build system: Rakefile cleanup
Build system: rename version/semantics

`version/conversions` is closer to the truth.
Build system: use SmartFileTask for package generation
Build system: OS X bundle tools
Build system: OS X bundle Rake tasks
Build system: use BundleEditorTask for bundle tweaking
Build system: get rid of InfoPlist helper

Superseded by `osx/plist` and its more `File#open`-like interface.
Build system: removed args property of SmartFileTask

As actions close over local vars, that did not make any sense. Pass
`self` instead.