Update sequel dependency to version 4.4.0

[rubik]

In Ruby 2.4.0, the old version of sequel gives annoying warnings about Fixnum and Bignum, which in the newer version of Ruby were unified into Integer:

$ t s
/home/user/.gem/ruby/2.4.0/gems/sequel-4.0.0/lib/sequel/database/schema_generator.rb:19: warning: constant ::Fixnum is deprecated
/home/user/.gem/ruby/2.4.0/gems/sequel-4.0.0/lib/sequel/database/schema_generator.rb:19: warning: constant ::Bignum is deprecated
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The last version of sequel fixes these.

[dashkb]

lol #155... @samg isn't ultra-responsive

[jostber]

Sequel is regularily updated, now in version 5.0.0. What about leaving this version dependency open so timetrap works with all versions?

[jostber]

Any news on this? I am packing timetrap for SlackBuild and the old sequel dependency gives a run error.

[dashkb]

Sounds like a good idea; I'd suggest opening the PR so if @samg thinks it's a good idea he can just merge it.

[berkes]

I've updated all dependencies and fixed the issues from that in #180