docs: Note that we need 0.15 (for estimatesmartfee with CONSERVATIVE/ECONOMCIAL flags)

Closes: #392
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

README.md

@@ -15,7 +15,7 @@ Don't hesitate to reach out to us on IRC at [#lightning-dev @ freenode.net](http
 
 ## Getting Started
 
-c-lightning currently only works on Linux (and possibly Mac OS with some tweaking), and requires a locally running `bitcoind` that is fully caught up with the network you're testing on.
+c-lightning currently only works on Linux (and possibly Mac OS with some tweaking), and requires a locally running `bitcoind` (version 0.15 or above) that is fully caught up with the network you're testing on.
 
 ### Installation
 

doc/INSTALL.md

@@ -10,8 +10,7 @@ For actually doing development and running the tests, you will also need:
 * asciidoc: for formatting the man pages (if you change them)
 * valgrind: for extra debugging checks
 
-You will also need a version of bitcoind with segregated witness support,
-such as the 0.13 or above.
+You will also need a version of bitcoind with segregated witness and estimatesmartfee economical node, such as the 0.15 or above.
 
 To Build on Ubuntu 15.10 or above
 ---------------------