[openvz] Fixes #1871 test helper callback

This moves the setting up of an `at_exit` callback from when the file
is required to when the matching helper is used.

This prevents it failing on any run where OpenVZ is excluded.
[rackspace|dns] fixing DNS pagination issue #1887
Merge branch 'master' of github.com:fog/fog into dns_page
Add SimpleCov and Coveralls.io dependenices
Add rake tasks for travis, which include publishing coverage reports.
Change travis to use a rake task instead of shindont directly.
This is partly necessary for
https://github.com/lemurheavy/coveralls-ruby/pull/20, though
I'm a fan of running just "rake" or "rake travis" for simplicity
anyways.
The actual simplecov/coveralls setup.
The use of Process.pid is an attempt to avoid confusing SimpleCov when
running tests in parallel.  Other tests frameworks take a similar
approach when they detect parallel_tests.
[rackspace|dns] added total_entries attribute to zones
[rackspace|dns] adding :limit => 100 to clarify that all returns a limit of 100 records per page at @rupakg suggestion.
Merge branch 'master' of github.com:fog/fog into dns_page
Initial documentation for using Fog with CloudSigma.
Fixed typos.
Update excon dependency to version ~>0.25.0
Merge pull request #1895 from rackspace/dns_page

[rackspace|dns] Fix Pagination in DNS
Merge pull request #1904 from sferik/update_excon_dependency

Update excon dependency to version ~>0.25.0
[vsphere] fix regex typo
Merge pull request #1908 from domcleal/regexp-typo

[vsphere] fix regex typo
Merge pull request #1872 from fog/fix_openvz_global_callback

[openvz] Fixes #1871 test helper callback
Merge pull request #1897 from maxlinc/code_coverage

Code coverage
[Brightbox] Updates to add collaborations

Adds requests and models for collaborations
[Brightbox] Extract Compute::Shared to own file

Seeing a lot of churn in lib/fog/brightbox/compute.rb because of adding
new requests or models as well as any implementation changes.

This moves the common behaviour between Compute's Real and Mock
classes into their own file to cut down on the noise when refactoring or
merging.