Initial adding of X.509 client certs
Adding documentation
Clarifying docs that client cert also should have key
Last time, getting the wording right.
Fixing the way we load the cert and key.

Turns out, you have to read the cert into Net::Http.cert.
Helps if I also document the environment vars...
Merge pull request #2612 from snackbandit/509

Initial support of X.509 client certificates
Require version file for checking capistrano version

bundler-1.4.0.pre.1 works fine, but bundler-1.4.0.pre.2 shows error below:
```
$ bundle exec cap production deploy
/path/to/bundler-1.4.0.pre.2/lib/bundler/capistrano.rb:7:in `<top (required)>': uninitialized constant Capistrano::Version (NameError)
```

This commit brings this error, so I add require version file.
1d7a7893dfeb85afa25a3a526354b31c85f05dbf

bundler: 1.4.0.pre.2
capistrano: 2.14.2
Guard from load error 'capistrano/version'
Simple check const exist
Merge pull request #2616 from sanemat/fix/if-capistrano

Require version file for checking capistrano version
extract Bundler.locked_gems
store parallel install count in settings
make symbol/string consistent for opts
Remove abort on exception
Errno::EPIPE has to be handled so as Thor::Base.start doesn't issue exit(0)

If for some reason pipe to which message is being written is closed that
causes a unhandled Errno::EPIPE exception which is handled by Thor itself
and Thor calls exit(0) whenever that happens.

This in turn prevents original exception to be printed because process exits
before it can print the message.
Handle unhandled exceptions for thread workers and enque a wrapped exception
Bring in fix introduced in PR#2622

Make sure thread index is passed when calling installer proc
Merge pull request #2623 from bundler/fix-thread-safety-parallel-install

Fix thread safety parallel install
require stuff we use