Fix exclusion of specs under 1.8.7

Due to VCR changing the format, the same recordings fail on 1.8.7 as are
recorded by later rubies.

A Rspec tag was added to exclude them but a glitch in the logic meant
these were not run for 1.8.7 or greater.
Exclude based on VCR tag

Major problem is 1.8.7 and VCR so we don't really need two tags since we
can just exclude every VCR tag.

Some curious cases where config errors are being raised only on Ruby
1.8.7 but not erroring on 2.1.0
Remove broken_1_8 tag now it is unused
Merge pull request #52 from brightbox/fix_18_exclusion

Fix exclusion of VCR specs that fail under 1.8.7