Custom reporter

Allow to use a custom reporter. If the config value is a string it uses one of the reporters included in the project.
Merge branch 'reporter_args' of github.com:piuccio/testem into piuccio-reporter_args
Added test and little cleanup.
0.4.8
Removed the `#testem` hash which is kinda deprecated, addresses #279.
0.5.0
Removed base_app.js
Removed base_app.js
Stop bundling tap.
Removed old filewatcher code.
Removed old version of bodydouble.
Rewrote process runner tests and removed dependenecy on bufferstream.
Updated tape version for the tape example.
Better test coverage for tap parsing and fix for #291.
0.5.1
0.5.2
Wrong browser ID when test page starts with a number
Corrected the fix.
0.5.3
Updates the Browserstack Integration Instructions

I had to hack through this a little bit, but it seems like the browserstack cli now has a setup command that generates the configuration file, which was much easier than trying to do it manually :)