Remove old Subtrees directory

src/.gitignore

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+# boost subtree
+/boost

src/README.md

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+# Subtrees
+
+These directories come from entire outside repositories
+brought in using git-subtree.
+
+About git-subtree:
+
+https://github.com/apenwarr/git-subtree <br>
+http://blogs.atlassian.com/2013/05/alternatives-to-git-submodule-git-subtree/ <br>
+
+## LevelDB
+
+Ripple's fork of LevelDB is shared by the Bitcoin reference client project.
+
+Repository <br>
+```
+git@github.com:ripple/LevelDB.git
+```
+Branch
+```
+ripple-fork
+```
+
+## LightningDB (a.k.a. MDB)
+
+A supposedly fast memory-mapped key value database system
+
+Repository <br>
+```
+git://gitorious.org/mdb/mdb.git
+```
+Branch
+```
+mdb.master
+```
+
+## websocket
+
+Ripple's fork of websocketpp has some incompatible changes and Ripple specific includes.
+
+Repository
+```
+git@github.com:ripple/websocketpp.git
+```
+Branch
+```
+ripple-fork
+```
+
+## protobuf
+
+Ripple's fork of protobuf doesn't have any actual changes, but since the upstream
+repository uses SVN, we have created a Git version to use with the git-subtree command.
+
+Repository
+```
+git@github.com:ripple/protobuf.git
+```
+Branch
+```
+master
+```
+
+**NOTE** Linux builds use the protobuf installed in /usr/lib. This will be
+fixed in a future revision.
+
+## SQLite
+
+Not technically a subtree but included here because it is a direct
+copy of the official SQLite distributions available here:
+
+http://sqlite.org/download.html