Check funds before popup metamask

[octavioamu]

Description

Add a balance checker before pops metamask to avoid people paying fees and then get stuck for the next payment.
Also it add featured to the math to check if the funder have enough funds.
Removes loading button state when fail to let the funder make changes and resubmit
https://embed.vidyard.com/share/FQJZYZDoX8q8wFgwMuBQSA?

Refers/Fixes

Fix #4618

Testing

Tested in rinkeby and mainnet (without completing the TX)
Tested with variations of using coupons with normal and 0 fees
Tested with featured bounties activated/deactivated
Tested with ETH and DAI

[codecov]

Codecov Report

Merging #4742 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #4742   +/-   ##
=======================================
  Coverage   30.44%   30.44%           
=======================================
  Files         216      216           
  Lines       17255    17255           
  Branches     2340     2340           
=======================================
  Hits         5254     5254           
  Misses      11793    11793           
  Partials      208      208

---

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[codecov]

Codecov Report

Merging #4742 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #4742   +/-   ##
=======================================
  Coverage   30.41%   30.41%           
=======================================
  Files         216      216           
  Lines       17240    17240           
  Branches     2335     2335           
=======================================
  Hits         5244     5244           
  Misses      11788    11788           
  Partials      208      208

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 8d1662c...bd50854. Read the comment docs.

[frankchen07]

cool, maybe in v2 we can increase the number of sig figs in the decimal amount (since it said you have 0.4 ETH but need 0.4 ETH (technically 0.4011 or something).

either way, the point is to warn them about amount, so this LGTM.

[danlipert]

@octavioamu I merged master into this branch and some random tests started failing :( not sure why