.gitignore: ignore editor swap files

Some source code editors create swap files in the same directory as the
file being edited. These should be ignored by git.
Fixed the library path for the x86_64 architecture
Documentation fixes

* amqp.h: Fix link to amqp_destroy_envelope()
* amqp_ssl_socket.h: Fix typo in parameter name
* amqp_tcp_socket.h: Use correct parameter name
* amqp.h: Typo in amqp_basic_ack() documentation
amqp.h: delivery mode constants

RabbitMQ defines two delivery modes, persistent and non-persistent, see
http://www.rabbitmq.com/amqp-0-9-1-reference.html#class.basic for more
information. This commit adds enumeration constants for these delivery
modes.
Switched to CMAKE_CURRENT_.. variants for source and binary dirs to enable nested builds.
Moved mutex initialization inside ENABLE_THREAD_SAFETY guards.
Right unexpected frames requeue in amqp_consumer.c
Use CMAKE_INSTALL_* variables provided by GNUInstallDirs.
Add GNUInstallDirs.cmake module

Adding GNUInstallDirs.cmake module for older versions of CMake that do not have
that module
Fix function amqp_get_monotonic_timestamp return zero

On one of my PC (Intel Core2 Duo Processor E7500 2.93 GHz),
QueryPerformanceFrequency return 2933330000.
This value  is greater than AMQP_NS_PER_S (1000000000).
Initial connection.blocked/unblocked support

Add encode/decode support for connection.blocked, connection.unblocked
RabbitMQ AMQP extension
Honor delivery mode value from command line

This change fixes a bug where delivery mode value was hardcoded to
"persistent" even when --persistent flag wasn't specified on the command
line options.
Improve documentation for amqp_ssl_socket_* funcs

Correctly document the return values that the amqp_ssl_socket_set_keys,
amqp_ssl_socket_set_cert, and amqp_ssl_socket_set_key_buffer functions
can return.

This fixes #155
Fixes librabbitmq.pc generation under autoconf

Properly substitute the @requires_private@ and @libs_private@ variables
when configuring under autoconf

This fixes #154
amqp_tcp_socket: update documentation

The socket is closed when amqp_connection_close() is called.

Signed-off-by: Luka Perkov <luka.perkov@sartura.hr>
Update README.md 

Include more completely instructions on how to build with autotools.
Preparation for v0.5.0 release
Bumping version for development
Add missing amqp_get_server_properties() function.

Fixes #170