Use more obvious example-bound values, cleanup README text

Sentinel Proxy version 2.1.0

Added
* log czmq with logc_czmq
* device token unit tests
* list of times of last received messages for each topic

Removed
* dev folder

Fixed
* device token library - inputs checks
* runnig unit tests in valgrind in no fork mode
* autotools warnings

Sentinel Proxy version 2.0.0

Added
* logc - logging support
* connected ZMQ peers monitoring
* check - unit tests
* cppcheck - linting
* lcov - code coverage
* valgrind
* Gitlab CI
* pkg-config and version scripts for device token library
* more fields in configuration file - it can hold the whole config now
* manual overall tests

Changed
* split server CLI option to server and port options
* CLI options - names, arguments and their descriptions updated

Sentinel Proxy version 1.4

Added
* Sending status messages to server
* Error messages

Removed
* Data compression

Sentinel-proxy version 1.3.1

Added
* Testing proxy - moved from Minipots repository
* CHANGELOG

Changed
* Complete code refactoring - replace `zpoller` by `zloop`

Implement crc check for device token

Fix segfault caused by MQTT handling

Implement device token

Fixup release

Initial release