Update README.md

Author: igrr

README.md

@@ -1,20 +1,28 @@
 Replacement for Espressif's libssl, kept as close as possible to [axTLS](http://axtls.sourceforge.net/) source.
 Currently based on axTLS 1.4.9, will be upgraded to 1.5.3.
 
+[![Build status](https://travis-ci.org/igrr/axtls-8266.svg)](https://travis-ci.org/igrr/axtls-8266)
+
 This is not a self-sufficient library. Application has to provide the following symbols (list not complete yet):
 ```
-malloc
-calloc
-free
-abort
+ax_port_malloc
+ax_port_calloc
+ax_port_realloc
+ax_port_free
+ax_port_read
+ax_port_write
+ax_port_open
+ax_port_close
+ax_get_file
+phy_get_rand  (provided by the IoT SDK)
+ets_printf    (in ESP8266 ROM)
+ets_putc      (in ESP8266 ROM)
 gettimeofday
 time
 ctime
-printf
-vprintf
 ```
 
-Additionally, functions for non-blocking TCP socket reads and writes have to be provided (details TBD).
+For use with LwIP raw TCP API, see [compat/README.md](compat/README.md)
 
 To build, add xtensa toolchain to your path, and run `make`.