feat(ethabi, token): support nested tuples/arrays parsing

[shekhirin]

Before

➜  ethabi git:(master) cargo run -- encode params -v '(bool,bool[])[]' '[(true,[false,true])]'
    Finished dev [unoptimized + debuginfo] target(s) in 0.04s
     Running `target/debug/ethabi encode params -v '(bool,bool[])[]' '[(true,[false,true])]'`
Error: Invalid data

➜  ethabi git:(master) cargo run -- encode params -v '(bool,bool[])' '(true,[false,true])' 
    Finished dev [unoptimized + debuginfo] target(s) in 0.11s
     Running `target/debug/ethabi encode params -v '(bool,bool[])' '(true,[false,true])'`
Error: Invalid data

After

➜  ethabi git:(parse-tuples-arrays) cargo run -- encode params -v '(bool,bool[])[]' '[(true,[false,true])]'
    Finished dev [unoptimized + debuginfo] target(s) in 0.04s
     Running `target/debug/ethabi encode params -v '(bool,bool[])[]' '[(true,[false,true])]'`
00000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000001000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000040000000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001

➜  ethabi git:(parse-tuples-arrays) cargo run -- encode params -v '(bool,bool[])' '(true,[false,true])'
    Finished dev [unoptimized + debuginfo] target(s) in 0.04s
     Running `target/debug/ethabi encode params -v '(bool,bool[])' '(true,[false,true])'`
000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000040000000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001

[vkgnosis]

CI fails because of cargo-fmt. I'm not familiar with this code (and I don't think anyone of the maintainers still is) but the test case makes sense to me and the change looks fine at a glance.

[shekhirin]

@nlordell hello sir, can I get your review on this PR?