Update README.md

README.md

@@ -9,7 +9,7 @@ A Julia package to work with [factor graphs](https://en.wikipedia.org/wiki/Facto
 
 ## Installation
 ```julia
-julia> ]add https://github.com/stecrotti/FactorGraphs.jl
+julia> import Pkg; Pkg.add(url="https://github.com/stecrotti/FactorGraphs.jl")
 ```
 
 ## Basics
@@ -61,4 +61,4 @@ Querying properties of a vertex without specifying whether it's a variable or a
 ```julia
 julia> outedges(g, 3)
 ERROR: ArgumentError: Properties of a vertex of an `AbstractFactorGraph` such as degree, neighbors, etc. cannot be accessed by an integer. Use a `variable` or `factor` wrapper instead.
-```
+```