Add VCR to run gem against actual confluence instance

Instead of stubbing, we can hit the actual SOAP API
Add pry
Wrap exceptions raised from #execute as ConfluenceSoap::Error

This allows easier integration for library users.  It is only necessary to rescue ConfluenceSoap::Error even if our underlying implementation changes.
Clean up Confluence space before test suite runs
Fix specs to use VCR instead of stubbing
Add yard for documentation
Make #execute private to hide session persistence

The gem user should not need to know that the session may expire from
time to time.  The gem handles renewing the session automatically
Update the README with instructions for running specs
Fix whitespace
Extract exception tagging logic into private method.
Handle repeated login failure case for #execute.
Ignore Bundler binstubs.
Merge pull request #1 from intridea/pmraw-84-improve-specs

Pmraw 84 improve specs