readme: Adapt to new test conditions and LuaJIT compatibility

Test 'NumberLimits' is not run previous to Lua 5.3, therefore the
message is obsolete.

User types do not work with LuaJIT 2.0.

README.md

@@ -142,7 +142,8 @@ point:x(4.2)
 
 ## Requirements
 You need a C++14-compliant compiler and at least Lua 5.1 to get this library to work. I recommend
-using Lua 5.3 or later, to avoid the messy `lua_Integer` situation. LuaJIT 2.0 seems to work aswell.
+using Lua 5.3 or later, to avoid the messy `lua_Integer` situation. LuaJIT 2.0 seems to work, apart
+from user types, which fail for yet unknown reasons.
 
 ## Tests
 The attached GNU `Makefile` allows you to run both examples and tests using `make examples` and
@@ -155,8 +156,3 @@ Assuming all headers are located in `/usr/include/lua5.3` and the shared object
 ```
 make LUA_INCDIR=/usr/include/lua5.3 LUA_LIBNAME=lua5.3 test
 ```
-
-Assertions relying on `lua_Integer` will fail, due to integer quirks in Lua. This should only
-concern you if your application expects Lua integers to work like normal integers, because they
-don't. Since integers are internally stored as floating-point numbers before Lua 5.3, you might
-consider treating them as such in your application.