Added definitions to docs

Author: kiranshila

docs/src/index.md

@@ -1,6 +1,13 @@
 # FresnelIntegrals.jl
 
-```@index
+A quick Julia library for calculating Fresnel Integrals using the error function from [SpecialFunctions.jl](https://github.com/JuliaMath/SpecialFunctions.jl).
+
+## Installation
+
+Until this is added into Pkg's manifest, just add from the Github link
+
+```julia
+Pkg.add("https://github.com/kiranshila/FresnelIntegrals.jl")
 ```
 
 ```@autodocs

src/FresnelIntegrals.jl

@@ -6,13 +6,15 @@ export fresnel
 
 """
         fresnelc(z)
-Calculates the Fresnel cosine integral for the number z
+Calculates the Fresnel cosine integral for the number z for
+    ``C(z) = \\int_{0}^{\\infty} \\cos{\\left(\\frac{\\pi t^2}{2}\\right)}``
 """
 fresnelc(z::Number) = 0.25*(1-1im)*(1im*erf(0.5*(1-1im)*z*√(π)) + erf(0.5*(1+1im)*z*√(π)))
 
 """
         fresnels(z)
-Calculates the Fresnel sine integral for the number z
+Calculates the Fresnel sine integral for the number z for
+    ``S(z) = \\int_{0}^{\\infty} \\sin{\\left(\\frac{\\pi t^2}{2}\\right)}``
 """
 fresnels(z::Number) = 0.25*(1+1im)*(-1im*erf(0.5*(1-1im)*z*√(π)) + erf(0.5*(1+1im)*z*√(π)))