Add a push method to push lead in marketo

[crabaux]

• Add push method in lead.js

push: function(input, options) {
if (!.isArray(input) && !.isEmpty(input)) {
var msg = 'input must be an array of leads';
log.error(msg);
return Promise.reject(msg);
}

var data = _.extend({}, options, {
  input: input
});

var path = util.createPath('leads', 'push.json');

return this._connection.postJson(path, data)
  .then(function(data) {
    if (data.success) {
      return data;
    } else {
      log.warn('Cannot push lead: ', data);
      return Promise.reject('Cannot get lead(s) from input: ' + JSON.stringify(input));
    }
  });

},

• Add documentation in the API doc API.md

lead.push(input, options)

Implements Push Leads

param	type	description
input	Array	An array of lead records to push
options	object
	lookupField: the field used to dedup on
	programName : the program name in Marketo

// Push a lead to Marketo program name
marketo.lead.push(
    [{'email': 'email@one.com'}, {'email': 'email@two.com'}],
    {lookupField: 'email', programName: 'Test program name'}
  )