Log Message:
Update ruby-bundler to 1.7.12.

## 1.7.12 (2015-01-08)

Bugfixes:

  - Always send credentials for sources, fixing private Gemfury gems (#3342, \ 
@TimMoore)

## 1.7.11 (2015-01-04)

Bugfixes:

  - Recognize `:mri_22` and `:mingw_22`, rather than just `:ruby_22` (#3328, @myabc)

## 1.7.10 (2014-12-29)

Bugfixes:

  - Fix source blocks sometimes causing deployment mode to fail wrongly (#3298, \ 
@TimMoore)

Features(?):

  - Support `platform :mri_22` and related version bits (#3309, @thomasfedb)

## 1.7.9 (2014-12-09)

Bugfixes:

  - Fix an issue where bundler sometime spams one gem in Gemfile.lock (#3216, \ 
@Who828)
  - Ensure bundle update installs the newer version of the gem (#3089, @Who828)
  - Fix an regression which stopped Bundler from resolving some Gemfiles (#3059, \ 
#3248, @Who828)

## 1.7.8 (2014-12-06)

Bugfixes:

  - Hide credentials while warning about gems with ambiguous sources (#3256, \ 
@TimMoore)

## 1.7.7 (2014-11-19)

Bugfixes:

  - Ensure server credentials stored in config or ENV will be used (#3180, \ 
@arronmabrey)
  - Fix race condition causing errors while installing git-based gems (#3174, \ 
@Who828)
  - Use single quotes in config so YAML won't add more quotes (#3261, @indirect)

## 1.7.6 (2014-11-11)

Bugfixes:

  - CA certificates that work with all OpenSSLs (@luislavena, @indirect)

## 1.7.5 (2014-11-10)

Bugfixes:

  - Fix --deployment with source blocks and non-alphabetical gems (#3224, @TimMoore)
  - Vendor CA chain to validate new rubygems.org HTTPS certificate (@indirect)

## 1.7.4 (2014-10-19)

Bugfixes:

  - Allow --deployment after `pack` while using source blocks (#3167, @TimMoore)
  - Use dependency API even when HTTP credentials are in ENV (#3191, @fvaleur)
  - Silence warnings (including root warning) in --quiet mode (#3186, @indirect)
  - Stop asking gem servers for gems already found locally (#2909, @dubek)