Introduce clojure-align-separator defcustom

[vemv]

Fixes #481

I'm not sure I used the type '(choice (const ... syntax correctly, since when I changed it using the value menu in M-x customize variable, the value of clojure-align-separator would appear unchanged (even though the widget says otherwise).

[Malabarba]

There's one quote too-many in the values of the choice spec.
The way you've defined it, the first value is the symbol clojure--align-separator-newline-regexp, and the second value is the list (quote entire).
I think you need to replace it with this:

`(choice (const :tag "Make blank lines prevent vertical alignment from happening."
                ,clojure--align-separator-newline-regexp)
         (other :tag "Allow blank lines to happen within a vertically-aligned expression."
                entire))

[vemv]

Thanks for the help! Tried out, works correctly. Commit amended.

:safe and :type values are missing because I couldn't find out the syntax for an option between symbol and regexp.

[vemv]

Status?

[bbatsov]

Ops, sorry about that. It completely slipped my mind. Thanks!

[vemv]

Thanks to you!

I noticed a typo in my commit (verical -> vertical)