On new job, issue NOTIFY via trigger.

This probably isn't done, as we need to tell people that they have to install
the new trigger function and the trigger if they want NOTIFY's to work
as they did before.

NOTIFY's are no longer issued by the queue_classic gem.
Use json type for the args column if json is available.

Also add some constraints to the q_name and method columns.
Merge pull request #136 from joevandyk/json

Use json type for the args column if json is available.
Bugfix: misspelling of word functions in tasks
Merge pull request #154 from tmock12/patch-1

Bugfix: misspelling of word functions in tasks
fix `QC::Conn#connect` when url has no host.

This is the case for the default url when running the tests:

        postgres:///queue_classic_test
Merge pull request #156 from ryandotsmith/fix_connect_for_url_without_host

fix `QC::Conn#connect` when url has no host.
Change log to report time elapsedin milliseconds
Merge pull request #151 from gregburek/uniform_log_time_calculation

Change how log_yield calculates time elapsed to match log
use json from the stdlib as MultiJson will be discontinued
Merge pull request #157 from ryandotsmith/use_stdlib_json

use json from the stdlib as MultiJson will be discontinued
refactor db wait into conn module
improve docs for enqueueing jobs
provide a default app_name. closes #158
Bugfix: It is simpler and less prone to error to set the name on the pg object.
add build status badge
add support docs in the readme
add benchmarks in test suite
make running bencmarks optional
subclasses of `PG::Connection` are fine too. Closes #161.