Added support for int64 data type

As influxdb now support data type specification for integers, in order
to separate those values from float64, this is a very simple solution.

Related to issue #48.

Steps:

• Added configuration option setForceIntegers
• Added data type doc
• Updated influxdb configuration for version 0.9.3
• Added force integers integration tests
• Refactored message to line protocol
• InfluxDB database version as env variable

Refactored message to line protocol functions

Actually the message_to_line_protocol function need the options set.
For that reason we have removed the helpers.php functions and moved
those utilities int the AdapterAbstract abstract base class.

InfluxDB integration test environment variable

In order to change the InfluxDB version we have prepared an env variable
in our Travis-CI configuration file .travis.yml

boolean data type management

In order to correctly supports boolean types, the library now will send "true" and "false" to Influxdb.

$client->mark("serie", [
  "is_valid" => true,
  "valve_open" => false,
]);

Maintanance release 0.6.2

Release

• Added tests against different Guzzle Versions (Extended compatibility list)
  • ~4
  • ~5
  • ~6
• Renamed wrong function prototype: inline protocol to line protocol

BC Breaks

The function message_to_inline_protocol now is renamed to message_to_line_protocol