Create CONTRIBUTING.md

Fixes #35
Merge pull request #34 from joujiahe/master

Make serialized stanza as a optional choice.
fix and test Stanza common attributes as properties
Merge pull request #37 from sonnyp/stanza

fix and test Stanza common attributes as properties
fix grunt jshint task to parse root .js files
Merge pull request #38 from sonnyp/Gruntfile

fix grunt jshint task to parse root .js files
Use 0.x version of `ltx`

See https://github.com/node-xmpp/node-xmpp-client/issues/42
Expose `ltx` via `node-xmpp-core`

See https://github.com/node-xmpp/node-xmpp-client/issues/42
Merge pull request #39 from node-xmpp/expose-ltx

Expose `ltx` via `node-xmpp-core`
Update versions
1.0.0-alpha1