add libsodium as dependency for building in readme

this finally got my debug-static-all to build. Obviously, its me, so this could use some edits or something.

README.md

@@ -172,6 +172,7 @@ library archives (`.a`).
 | OpenSSL        | basically any | NO       | `libssl-dev`       | `openssl`      | NO       | sha256 sum     |
 | libzmq         | 3.0.0         | NO       | `libzmq3-dev`      | `zeromq`       | NO       | ZeroMQ library |
 | libunbound     | 1.4.16        | YES      | `libunbound-dev`   | `unbound`      | NO       | DNS resolver   |
+| libsodium      | ?             | NO       | `libsodium-dev`    | ?              | NO       | libsodium      |
 | libminiupnpc   | 2.0           | YES      | `libminiupnpc-dev` | `miniupnpc`    | YES      | NAT punching   |
 | libunwind      | any           | NO       | `libunwind8-dev`   | `libunwind`    | YES      | Stack traces   |
 | liblzma        | any           | NO       | `liblzma-dev`      | `xz`           | YES      | For libunwind  |
@@ -182,6 +183,7 @@ library archives (`.a`).
 | Doxygen        | any           | NO       | `doxygen`          | `doxygen`      | YES      | Documentation  |
 | Graphviz       | any           | NO       | `graphviz`         | `graphviz`     | YES      | Documentation  |
 
+
 [^] On Debian/Ubuntu `libgtest-dev` only includes sources and headers. You must
 build the library binary manually. This can be done with the following command ```sudo apt-get install libgtest-dev && cd /usr/src/gtest && sudo cmake . && sudo make && sudo mv libg* /usr/lib/ ```