added instructions to build on Fedora/Centos

docs/build_notes_unix.md

@@ -5,6 +5,7 @@ First of all we need to make sure that all dependencies are satisfied.
 
 This doc is trying to cover:
 * [Debian/Ubuntu](#debianubuntu) (contains packaging instructions)
+* [Fedora/Centos](#fedoracentos)
 * [FreeBSD](#freebsd)
 
 Make sure you have all required dependencies for your system successfully installed.
@@ -56,6 +57,35 @@ cd i2pd
 debuild --no-tgz-check
 ```
 
+Fedora/Centos
+-------------
+
+You will need a compiler and other tools to perform a build:
+```bash
+sudo yum install make cmake gcc gcc-c++
+```
+
+*Latest Fedora system using [DNF](https://en.wikipedia.org/wiki/DNF_(software)) instead of YUM by default, you may prefer to use DNF, but YUM should be ok*
+
+> *Centos 7 has CMake 2.8.11 in the official repositories that too old to build i2pd, CMake >=2.8.12 is required*
+> You could build CMake for Centos manualy(WARNING there are a lot of build dependencies!):
+> ```bash
+> wget https://kojipkgs.fedoraproject.org/packages/cmake/2.8.12/3.fc21/src/cmake-2.8.12-3.fc21.src.rpm
+> yum-builddep cmake-2.8.12-3.fc21.src.rpm
+> rpmbuild --rebuild cmake-2.8.12-3.fc21.src.rpm
+> yum install ~/rpmbuild/RPMS/x86_64/cmake-2.8.12-3.el7.centos.x86_64.rpm
+> ```
+
+Also you will need a bunch of development libraries
+```bash
+sudo yum install boost-devel openssl-devel
+```
+
+If you need UPnP support (don't forget to run CMake with `WITH_UPNP=ON`) miniupnpc development library should be installed:
+```bash
+miniupnpc-devel
+```
+
 FreeBSD
 -------