update readme with quick start

README.md

@@ -8,14 +8,38 @@ Small toolbox for Isogeometric analysis. Built on top of [Ferrite](https://githu
 
 ## Installation
 
+Currently only works on Ferrite master branch
+
 ```
-pkg> add https://github.com/lijas/IGA.jl.git
+Pkg.add(url="https://github.com/Ferrite-FEM/Ferrite.jl",rev="master")
+Pkg.add(url="https://github.com/lijas/IGA.jl",rev="master")
 ```
 
 [docs-dev-img]: https://img.shields.io/badge/docs-dev-blue.svg
 [docs-dev-url]: https://lijas.github.io/IGA.jl/dev/
 
-## About IGA
+## Quick start
+The API is similar to Ferrite.jl:
+
+```
+using Ferrite, IGA
+
+order = 2 # second order NURBS
+nels = (20,10) # Number of elements
+patch = generate_nurbs_patch(:plate_with_hole, nels, order) 
+
+#Convert nurbs patch to a Grid structure with bezier-extraction operators
+grid = BezierGrid(patch)
+
+#Create interpolation and shape values
+ip = IGAInterpolation{RefQuadrilateral,order}() #Bernstein polynomials
+qr_cell = QuadratureRule{RefQuadrilateral}(4)
+
+cv = BezierCellValues(qr_cell, ip, update_hessians=true)
+
+#...
+#update cell values
+coords::BezierCoords = getcoordinates(grid, 1)
+reinit!(cv, coords)
 
-From wikipedia: 
-*Isogeometric analysis is a computational approach that offers the possibility of integrating finite element analysis (FEA) into conventional NURBS-based CAD design tools. Currently, it is necessary to convert data between CAD and FEA packages to analyse new designs during development, a difficult task since the two computational geometric approaches are different. Isogeometric analysis employs complex NURBS geometry (the basis of most CAD packages) in the FEA application directly. This allows models to be designed, tested and adjusted in one go, using a common data set.*
+```