use DataFrames as input for `performance_profile()`

Using data frames from [DataFrames.jl](https://github.com/JuliaData/DataFrames.jl) as input for `performance_profile()` would be usefull.
Perhaps, the syntax could be to have a DataFrame as
``` julia
df = DataFrames(ProbName=String[],Solver1=Int[],Solver2=Int[],Solver3=Int[])
```
then push to `df` the data from each solver and call
```julia
performance_profiles(df)
```
which would use the column name from `df` as name of the solver, if note given by the user.