Set bundle options before check via bundle config

[spajic]

Hello, @mattbrictson !

This PR is advances idea, discussed in #97

Here I take two more options into account: bundle_frozen and bundle_disable_shared_gems

97 still has problem I'm trying to solve here, setting 3 options is happened to be not enough.

# default values for new options
set :bundle_frozen, '1'
set :bundle_disable_shared_gems, true

Now I set 5 bundle config options before bundle check:

execute :bundle, :config, "--local path #{bundle_path}" if bundle_path
execute :bundle, :config, "--local without #{bundle_without.split(' ').join(':')}" if bundle_without
execute :bundle, :config, "--local gemfile #{bundle_gemfile}" if bundle_gemfile
execute :bundle, :config, "--local frozen #{bundle_frozen}" if bundle_frozen
execute :bundle, :config, "--local disable_shared_gems #{bundle_disable_shared_gems}" if bundle_disable_shared_gems

Code from this PR is battle-tested, we already use it in production.

Though we are adding 5 more commands, we still have order-of-magnitude win. bundle command may take more than 25 seconds to fetch metadata.

5 bundle config commands take about 1,5 seconds for us in deploy to 3 app-servers with 50ms ping.

With faster ping 5 bundle config will take even less time.

[capistrano-bot]

	1 Warning
:warning:	Please update CHANGELOG.md with a description of your changes. If this PR is not a user-facing change (e.g. just refactoring), you can disregard this.

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Here's an example of a CHANGELOG.md entry (place it immediately under the * Your contribution here! line):

* [#101](https://github.com/capistrano/bundler/pull/101): Set bundle options before check via bundle config - [@spajic](https://github.com/spajic)

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[spajic]

@mattbrictson May be it would be better to combine 5 config commands into 1? What do you think?

[mattbrictson]

Closing in favor of #122