Electron semantics, lookup json and fixes

Adds:

• Electron configuration semantic key added
• Lookup json for easy indexing
• Add electronegativity and other electronic properties

Fixes:

• Typo fixes
• Corrected some numbers
• Electron configurations are now ordered in a more conventional order

Again, thanks for everyone who opened a PR :D

Electron Shells

Minor fixes:
Added electron shells
Made number an int instead of a string

Revised JSON, now formatted as an array and has new elements

Merge pull request #14 from aarjithn/master

Reformat JSON to array of elements

Periodic Table JSON

Inital release of the periodic table JSON