Add table enhancements and owner validation

[radchukd]

Closes #43, #44, #45

[radchukd]

PR is a bit big, here's a summary:

1. Contexts
I added 2 contexts - OwnersContext and TransactionsContext, which provide data respectively and handle all the smart contract interactions, in result:

• removed code repetition;
• added single source of truth with easier access to it;
• added separation between data and UI;
• made loading more predictable;
• made table manipulation possible.

2. Table
I added react-table library (MIT) to handle sorting and pagination in the transactions table.

3. Other
I changed the ReplaceOwnerModal according to #43.
I did everything in #44 (added jazzicon component, owner validation, renaming).

[apbendi]

Hey @radchukd, looking great overall! A couple things I've noticed:

• Sorting seems to be broken. Clicking the headers makes the table flicker, but the sorting order/column does not change
• The "Show N" dropdown works well, but it should only show up if the wallet has more than 5 txs to display. Before that point, it should be hidden.

[apbendi]

There also seems to be some kind of state bug occurring when navigating between wallets. Here's a brief example:

[radchukd]

Now also closes #47

[apbendi]

Hey @radchukd, sorting and threshold button changes looking good! However, I am still seeing the state issues in the UI when switching between wallets. Note how when I start with an empty wallet, switch to one with lots of txs, then navigate back to the empty wallet, I see empty tables displayed. When I refresh, it looks the way it should:

[apbendi]

@radchukd looks like there's a regression on the "Change Threshold" form validation. Not accepting anything other than 1, even when there are multiple owners:

[radchukd]

Oops, the problem was in a totally different place, sorry. I reverted the previous changes and pushed a new commit, should be good now.

[apbendi]

Hey @radchukd, the state issues I was seeing when navigating between wallets seems to be resolved, though I'm now seeing a similar issue when creating a new tx. Check it out:

[radchukd]

@apbendi should be good now.