Dynamic index support for elasticsearch

[kolomiets]

Dynamic indeces are much more flexible, so it log entry has a timestamp
(typically it does) - we can build dynamic index name for elasticsearch.

[coveralls]

Coverage decreased (-0.7%) to 99.329% when pulling 9381f92 on hazy-bits:elasticsearch-dynamic-index-support into 729f9ba on arithmetric:master.

[kolomiets]

Ups, sorry for that, will fix all the issues shortly.

[coveralls]

Coverage remained the same at 100.0% when pulling da2490d on hazy-bits:elasticsearch-dynamic-index-support into 729f9ba on arithmetric:master.

[myoung34]

@kolomiets i was able to do this without using any code changes:

var moment = require('moment')

then in my configuration:

            elasticsearch: {
              index: 'lambda-' + moment().format('YYYY-MM-D'),
              type: 'test'
            }