Fix ArgumentError.

[vakuum]

The following line in lib/http/cookie_jar/abstract_store.rb cause an ArgumentError:

raise IndexError, 'cookie store unavailable: %s, error: %s' % symbol.inspect, e.message

The parameters of the % operator must be passed as an array:

raise IndexError, 'cookie store unavailable: %s, error: %s' % [symbol.inspect, e.message]

Without this change:

> HTTP::Cookie::VERSION
 => "1.0.4" 

> HTTP::CookieJar.new(store: :unknown)
...
ArgumentError (too few arguments)

With this change:

> HTTP::Cookie::VERSION
 => "1.0.4" 

> HTTP::CookieJar.new(store: :unknown)
...
ArgumentError (cookie store unavailable: :unknown, error: cannot load such file -- http/cookie_jar/unknown_store)

[julien-pinchelimouroux]

Why is this PR not already merged ?
We have the same issue in production based on RestClient http-cookie usage.

This is also fixed by #43

[flavorjones]

This was fixed in 44374a7