Genericize the concept of network operations

Instead of calling these "downloads" and naming them off of the
net_download() method, these can be called "netops" and be their own
interface.

Doing so will allow the splitting of net_download() up so that there can
be separate methods (e.g. net_string() or similar).
Split apart net_download() method

Creates a separate net_stream() method that has a similar interface but
just returns the raw string to the caller.
Introduce net_dump() method for services

This new method will allow a service to grab some sort of arbitrary
stream content from the Internet and save it to a raw audio file. This
operation counts as a network operation for the purposes of throttling.
Initial implementation of ImTranslator

This is a complete implementation, save for sending requests over POST
instead of GET.
Add POST mode ability for net_stream()

This also enables it for net_download(), if the need comes up.

ImTranslator will now use POST.
Introduce util_merge() for services

Allows several files to be merged into one.
ImTranslator support for very long phrases

Adds support for AwesomeTTS to retrieve 400+ character input phrases
from ImTranslator.
Improved transform/values for ImTranslator speed

Only maps down to the actual speeds ImTranslator has and use a min()
function with a key specified to normalize user input to the closest
one.
Windows fixes for net_dump()

On Windows, the filename must be quoted and specifying 'null' for -vo
causes the playback to cut early (but any other value seems to work).
Update documentation for ImTranslator

Adds to README, rewords throttling information on the configuration
screen, and adds page to the website.
Disable ImTranslator for Mac OS X

Turns off ImTranslator specifically for Mac OS X.

The audio dump on OS X is very buggy, and usually just results in
mplayer crashing.
Merge branch 'add/imtranslator' into develop

Adds the ImTranslator service.