Addressed issue #127.

See new get_int method.
Fixed bug in get_int (thanks Travis for reporting the bug).
Optimized get_int by adding exit condition.
Adjusted sd_vector test to capture special case.
Initialization is out of bounds.
Simplified code.
Implemented get_int for remaining bitvectors.
Merge pull request #128 from simongog/bv_access

Addressed issue #127 for all bitvectors.
added bwt option to testcase.config
Merge branch 'benchmark_wt' of https://github.com/xosh/sdsl-lite into benchmark_wt

Conflicts:
	benchmark/wavelet_trees/test_case.config
	benchmark/wavelet_trees/wt.config
fixed a bug in Make.download
Merge branch 'master' of https://github.com/simongog/sdsl-lite into benchmark_wt

Conflicts:
	benchmark/wavelet_trees/Makefile
	benchmark/wavelet_trees/src/gen_bwt.cpp
Added integer testcase, reduced repeats of interval_symbols on inputs with large alphabets
added peak memory usage functionality to memory manager
Fixed accuracy in construction time.
Added Elias gamma coder.

Using gamma code was suggested in Grossi, Gupta, Vitter (SODA 2004).
Thanks to Kunihiko Sadakane for pointing this out.
Fixed warning in CLANG.
Merge pull request #132 from simongog/fix_warning

Fixed warning in CLANG.
Handled implicit conversion.
Merge pull request #129 from xosh/benchmark_wt

Benchmark wt