fix a few typos
Merge pull request #2003 from givanse/typos

fix a few typos
[DOC] Add note about expected JSON for ActiveModelAdapter relationships

This is covered in the recently added example, but not explicit.
Merge pull request #2006 from Dave-Choi/patch-1

[DOC] Add note about expected JSON for ActiveModelAdapter relationships
better error for missing inverse on hasMany/belongsTo
Merge pull request #2009 from knownasilya/inverse-msg

better error for missing inverse on hasMany/belongsTo