attachment clarification
correction
Merge pull request #168 from bscSCORM/attachment

DISCUSS: attachment clarification
eventual consistancy

* Created a section for common requirements when PUT-ing or POST-ing statements,
moved existing common requirements to that section
* Added eventual consistancy requirements
switched upconversion prefix from urn: to tag: as decided on call
Merge pull request #172 from bscSCORM/conversion

switched upconversion prefix from urn: to tag: as decided on call
Merge branch 'master' of https://github.com/adlnet/xAPI-Spec
tidy up
Merge pull request #171 from bscSCORM/eventual

eventual consistancy
Merge pull request #177 from fugu13/tidyup

Just a small bit of tidying up