Rename strophe.mam.js to strophe.mam.v0.2.js
Create strophe.mam.v0.3.js

the standards for XEP-0313 have changed, this new code makes MAM work as intended with servers (such as prosody) that have migrated to the new standard.  Could use some improvements like preferences, but in my case i don't need them yet.
Update strophe.mam.v0.3.js

Updated Comment in top to reflect modified by and modification purpose.
Merge pull request #37 from Destreyf/master

Support v0.3 of XEP-0313 (MAM)