[Unit Testing] Added test that checks correct behavior when connection fails and there is no connections left in the pool.
[Comments] More comments added.
[Unit Testing] Added test that checks correct behavior when connection error occurs and there is no attempts left.
[Unit Testing] Added test that checks correct behavior when performing request while the pool is empty.
[Documentation] Drop deprecated comments.
[Unit Testing] Added test that checks successful sniffing on error.
[GCC 4.4] Fix.
[Unit Testing] Added test that checks correct behavior when sniffing fails.
[Code Style] A bit.
[Unit Testing] Some tests added.
[Unit Testing] Another pack of transport tests added.
[Unit Testing] Tests for bulk write and nodes info actions added.
[GCC 4.4] Fixed build on ancient compilers.