rescue from IOError and terminate the connection

contrary to what was probably assumed, IOError is not a SocketError...

Closes #295

lib/httpx/connection.rb

@@ -522,7 +522,8 @@ module HTTPX
            Errno::ENETUNREACH,
            Errno::EPIPE,
            Errno::ENOENT,
-           SocketError => e
+           SocketError,
+           IOError => e
       # connect errors, exit gracefully
       error = ConnectionError.new(e.message)
       error.set_backtrace(e.backtrace)

lib/httpx/io/tcp.rb

@@ -78,7 +78,8 @@ module HTTPX
     rescue Errno::ECONNREFUSED,
            Errno::EADDRNOTAVAIL,
            Errno::EHOSTUNREACH,
-           SocketError => e
+           SocketError,
+           IOError => e
       raise e if @ip_index <= 0
 
       log { "failed connecting to #{@ip} (#{e.message}), trying next..." }