replaced indexOf with startsWith where required to improve performace

[clintonyeb]

The source code makes a lot of checks to make sure a string starts with *0x". If this is true, the string is treated as a hash value or a number otherwise.

However using indexOf to test for this is inefficient as compared to its equivalent startsWith.

Here is a small benchmark test:

Here is the GitHub Gist: web3_indexof_starts_with.js

To verify the results, run:

$ node web3_indexof_starts_with.js

Testing startsWith:::
Benchmark took 1834165 nanoseconds
Completed startsWith.

Testing indexOf:::
Benchmark took 2679461 nanoseconds
Completed indexOf.

Thanks.

[coveralls]

Coverage remained the same at 90.476% when pulling 4210dfb on clintonyeb:develop into 215e33c on ethereum:develop.

[nivida]

It would be cool if you could submit also a PR for the 1.0 version. If you will do this then please to it in the ethereumProvider branch because the architecture of web3.js has changed a lot there :)

[nivida]

Closed because the latest maintenance release was 0.20.7.