set -O2, removed -g flags to GCC

Also fixed Erlang coverage flag.

With -O2, after several runs to prime cache:

8> quoted:test_2kb(50).
['Decode 2KB quoted string',
 {test_type,nif_impl,erl_impl},
 {list_to_list,28.36,415.74},
 {list_to_bin,22.86,423.8},
 {bin_to_bin,7.4,472.06},
 {bin_to_list,11.08,468.94},
 'Encode 2KB quoted string',
 {test_type,nif_impl,erl_impl},
 {list_to_list,83.08,752.6},
 {list_to_bin,35.88,800.34},
 {bin_to_bin,18.62,889.64},
 {bin_to_list,62.08,888.66}]

Without:

15> quoted:test_2kb(50).
['Decode 2KB quoted string',
 {test_type,nif_impl,erl_impl},
 {list_to_list,44.82,420.0},
 {list_to_bin,39.28,419.22},
 {bin_to_bin,23.86,470.44},
 {bin_to_list,28.36,468.78},
 'Encode 2KB quoted string',
 {test_type,nif_impl,erl_impl},
 {list_to_list,128.52,753.38},
 {list_to_bin,70.68,800.42},
 {bin_to_bin,55.36,889.64},
 {bin_to_list,97.86,1004.28}]
encode spaces as +-characters
re-add nif implementation
compiling with hipe fails with -on_load attributes
re-add on_load and adjust nif to "new" api
reordered bool checks in order of probability
decode '+' as ' ', but not vice versa
delegate to exported fallback functions
simple search-replace of calls
replace %20 with + in test cases
Merge branch 'nif' into merge

Conflicts:
	rebar.config (coverage flag typo)
updated tests to match new export names
Merge pull request #1 from pivotree/merge

NIF handles '+'->' '
Minor optimization
-O2 flag
Merge branch 'master' of github.com:klaar/quoted.erl

Conflicts:
	test/quoted_tests.erl
Add stub functions for module upgrades
bump version
Add Apache licence and copyright boilerplate
don't use agner rebar plugin, not using any deps
clean up function to check safe characters
Ensure that both characters after % are valid