[xml-conduit] Minor optimizations

Please find enclosed some minor performance improvements I've done to the XML parsing part of xml-conduit. For a simple criterion benchmark of `runException $ sourceList [t] $$ parseText def =$= sinkNull` with `t` being a simple [sample XML](http://msdn.microsoft.com/en-us/library/windows/desktop/ms762271%28v=vs.85%29.aspx) the results are as follows:

benchmarking original
mean: 810.2672 us, lb 808.6924 us, ub 812.3712 us, ci 0.950
std dev: 9.245363 us, lb 7.303553 us, ub 12.14877 us, ci 0.950

benchmarking optimized
mean: 707.9308 us, lb 706.3906 us, ub 709.8012 us, ci 0.950
std dev: 8.634447 us, lb 7.389908 us, ub 10.45892 us, ci 0.950

That is, roughly a 12% improvement. For good measure I also renamed the REAMDE file to README and applied a few hlint suggestions that seemed appropriate.