Merge pull request #878 from anandijain/aj/docs

fix docstring syntax highlighting

Author: ChrisRackauckas

src/systems/control/controlsystem.jl

@@ -30,7 +30,7 @@ $(FIELDS)
 
 # Example
 
-```
+```julia
 using ModelingToolkit
 
 @variables t x(t) v(t) u(t)

src/systems/diffeqs/odesystem.jl

@@ -8,7 +8,7 @@ $(FIELDS)
 
 # Example
 
-```
+```julia
 using ModelingToolkit
 
 @parameters t σ ρ β

src/systems/diffeqs/sdesystem.jl

@@ -8,7 +8,7 @@ $(FIELDS)
 
 # Example
 
-```
+```julia
 using ModelingToolkit
 
 @parameters t σ ρ β

src/systems/nonlinear/nonlinearsystem.jl

@@ -8,7 +8,7 @@ $(FIELDS)
 
 # Examples
 
-```
+```julia
 @variables x y z
 @parameters σ ρ β
 

src/systems/optimization/optimizationsystem.jl

@@ -8,7 +8,7 @@ $(FIELDS)
 
 # Examples
 
-```
+```julia
 @variables x y z
 @parameters σ ρ β
 

src/systems/reaction/reactionsystem.jl

@@ -9,7 +9,7 @@ $(FIELDS)
 
 # Examples
 
-```
+```julia
 using ModelingToolkit
 @parameters t k[1:20]
 @variables A(t) B(t) C(t) D(t)
@@ -117,7 +117,7 @@ $(FIELDS)
 
 # Example
 Continuing from the example in the [`Reaction`](@ref) definition:
-```
+```julia
 rs = ReactionSystem(rxs, t, [A,B,C,D], k)
 ```
 """