Select with {key: value} style options

[zdenko]

This PR enables use of key: value style options for the select field. And, as a bonus, adds Coffeescript 2.

template = makeTemplate """
  select(@value @options)
"""

options = Observable
  nap: "Napoleon"
  bar: "Barrack"

model =
  options: options
  value: "bar"

select = template model

assert.equal select.value, "bar"

# adding an option
options Object.assign {}, options(), {test: "Test"}
assert.equal select.querySelectorAll("option").length, 3

# deleting an option
delete options().test
options Object.assign {}, options()
assert.equal select.querySelectorAll("option").length, 2

Observable value

template = makeTemplate """
  select(@value @options)
"""

options = Observable
  nap: Observable "Napoleon"
  bar: Observable "Barrack"

model =
  options: options
  value: "bar"

select = template model

optionElements = select.querySelectorAll("option")
assert.equal optionElements[1].textContent, "Barrack"
options().bar "YOLO"
assert.equal optionElements[1].textContent, "YOLO"

With the PR from distri/observable adding and deleting option can be shorter:

# adding an option
options.extend {test: "Test"}

# deleting an option
options.remove "test"