Add Tutorial Mode

[ahyork]

Allows the user to enter tutorial mode and experiment with the package. It sets their PATH_TO_DATA to our testing data folder. With this, we can adjust the the demos and highlights of our code so that someone in tutorial mode can recreate exactly what we are showing.

[coveralls]

Pull Request Test Coverage Report for Build 143

• 9 of 12 (75.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.2%) to 87.382%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/PorousMaterials.jl	9	12	75.0%
<!--	Total:	9	12	75.0%	-->

Totals
Change from base Build 126:	-0.2%
Covered Lines:	741
Relevant Lines:	848

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💛 - Coveralls

[SimonEnsemble]

dirname(pathof(PorousMaterials)) nice.

how about set_path_to_data(new_path_to_data::String) as well?

i do like the warning abt when the data directory doesn't exist to some extent, but I think this might make the software less flexible. what if I want to load in a JLD object instead of from a file? no need for data directory. what if I want to using PorousMaterials and then make the data directory, or if I want to change the PATH_TO_DATA to somewhere else after using PorousMaterials? this checking for path and throwing error would not allow this. is that right?

[ahyork]

I changed it back to throw warnings instead, just to let the user know that PorousMaterials doesn't detect a folder at the time the PATH_TO_DATA is loaded or changed. Should the default for the PATH be pwd * "/data/"? I can change the wording on the warnings to be more specific like No data folder found in pwd. PorousMaterials will not be able to load any crystals, forcefields, or molecules with the current PATH_TO_DATA I can make that new function quickly and throw in some tests for it as well.

[SimonEnsemble]

good to change to warning instead of error.

yep, default is pwd() * "/data" in master right?

How about something like: @warn @sprintf("Directory for input data,data, not found in present working directory, %s\nChange thePATH_TO_DATAvariable to load input files from a different directory. Seeset_path_to_data().\n", pwd())

[ahyork]

That looks good, I'll do that.