Implement ACKNOWLEDGED property.

  http://tools.ietf.org/html/draft-daboo-valarm-extensions-04
Outputs version before anything else for base VCALENDAR
Merge pull request #24 from tsuzuki08/acknowledged-extention

Implement ACKNOWLEDGED property.
Merge pull request #25 from rahearn/version-first

Outputs version before anything else for base VCALENDAR
Only outputs timezone info for transitions that are present

fixes #21
Bumps to 1.4.0
GEO property excluded from being escaped
Merge pull request #30 from temirov/master

Semicolon for GEO property should not be escaped
Adds .ruby-* files to gitignore
Updates conversion test to accound for un-escaped ; in geo property
Use "def self." for class methods
Style cleanups
Allows access to various rrule parts

closes #27
Bumps version to 1.4.1
Removes rubyforge infrastructure

closes #19
Cleans up README
Removes unnecessary cruft
Document the use of `icalendar_tzid` a little bit

issue #33
Update Component#respond_to? to match ruby 2.0 signature

Since it is only the additional optional attribute, it should have no impact aside from silencing warnings in rspec-mocks and ruby 2.0.
Merge pull request #37 from kamarcum/patch-1

Update Component#respond_to? to match ruby 2.0 signature