Minor refactoring
First Cut of Table Formulas
Updated Table Formulas

- Added single function for both command & mapping to take formula from
  input.
- Reusing g:table_mode_align for formatting table content, which was
  missed when moving from :Tableize to tabular#TabularizeStrings
- Correctly parsing ranges as strings.
Removed dependence on Tabular for more control.

- Right align numbers automatically.
Fine tuning & formatting
Merge branch 'master' of github.com:dhruvasagar/vim-table-mode into feature/table-formulas

Conflicts:
	autoload/tablemode.vim
Releasing v3.0

- Added feature to define & add formula expressions to table and
  calculate them.
- Persist the fomulas as comments as line right after table.
Merge branch 'feature/table-formulas'
Updated README.md
Updated CHANGELOG & doc/table-mode.txt